Substituted isoxazolopyridazinones and isothiazolopyridazinones and methods of use

ABSTRACT

Compounds of formula (I) 
     
       
         
         
             
             
         
       
     
     and pharmaceutically acceptable salts thereof, wherein R 1 , R 2  and R 3  are as defined in the specification, are useful in treating conditions or disorders prevented by or ameliorated by positive allosteric modulation of the γ-aminobutyric acid B (GABA-B) receptor. Methods for making the compounds are described. Also described are pharmaceutical compositions of compounds of formula (I), and methods for using such compounds and compositions.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority to International PatentApplication No. PCT/CN2015/089614, filed on Sep. 15, 2015, and EuropeanPatent Application No. 15193907.1, filed Nov. 10, 2015. The entirecontents of these applications are incorporated by reference into thispatent application.

BACKGROUND OF THE INVENTION

Technical Field

The invention relates to substituted pyrazolopyrimidines that arepositive allosteric modulators of the γ-aminobutyric acid receptor(e.g., GABA-B PAM), useful in treating diseases and conditions mediatedand modulated by the γ-aminobutyric acid receptor B. Additionally, theinvention relates to compositions containing compounds of the inventionand processes of their preparation.

Description of Related Technology

The inhibitory neurotransmitter, γ-aminobutyric acid (GABA) exerts itsactions through three distinct receptors—the ionotropic GABA-A andGABA-C receptors, and the metabotropic GABA-B receptor. The GABA-Breceptor is a member of the class C family of GPCRs. The GABA-B receptoris an obligate heterodimer composed of a GABA-B1 and a GABA-B2 subunit(Bettler, B., et al. Physiol Rev 2004; 84: 835-867). Notably,heterodimerization of the B1 and B2 subunits is required for properGABA-B receptor expression and function (Pin, J. P., et al. BiochemPharmacol 2004; 68: 1565-1572). Agonist binding to the B1 subunit of theGABA-B heterodimer results in transactivation of the B2 subunit andsubsequent stimulation of G_(i/o) proteins. This, in turn, activates K⁺currents, inhibits Ca²⁺ currents, and decreases cAMP via negativeregulation of adenylyl cyclase.

GABA-B receptor subunits are found both pre- and post-synapticallythroughout the CNS and the periphery, with highest expression in thethalamus, cortex, cerebellum and dorsal horn (Fritschy, J. M., et al.Eur J Neurosci 1999; 11: 761-768). Functional receptor expressionappears to be limited by the presence of the GABA-B2 subunit, which isoften detected at lower levels than the B1 subunits (Bowery, N. G. AdvPharmacol 2010; 58: 1-182). Therapeutically, the beneficial effects ofGABA-B receptor stimulation include muscle relaxation, substance abusetreatment (especially in alcohol dependence), antinociception,spasticity, fragile X syndrome, Down's syndrome, autism, retinalganglion cell degeneration, gastro-esophageal reflux disease (GERD),smoking cessation, addiction of narcotic agents, emesis, cough,overactive bladder, anxiety, migraine or tinnitus. The in vivoconsequence of GABA-B activation has been confirmed experimentally withknockout mouse models, which are hyperalgesic, and clinically with theGABA-B orthosteric agonist, baclofen (Slonimski, M., et al. Reg AnesthPain Med 2004; 29: 269-276. Bowery, N. G., et al. Pharmacol Rev 2002;54: 247-264). Unfortunately, the utility of baclofen is limited by drugtolerance and severe side effects, including hypothermia, seizures,sedation and cognitive deficits. Baclofen has poor brain penetrance andrequires high doses for engagement of CNS GABA-B receptors, resulting inelevated plasma concentrations. Peripheral GABA-B receptors on smoothand skeletal muscle are activated by these high plasma concentrationsand appear to mediate a subset of baclofen side effects, includinghypothermia and seizures that are hypothesized to arise from erraticmuscle contractions. Drug tolerance requiring dose escalation has beenreported three to seven days after initiation of baclofen and mostlikely arises from receptor desensitization (Sands, S. A., et al. JPharmacol Exp Ther 2003; 305: 191-196). This reduction in GABA-Breceptor signaling mimics the genotype of GABA-B knockout mice, whichalso exhibit severe cognitive and learning deficits (Schuler, V., et al.Neuron 2001; 31: 47-58). Tolerance and receptor desensitizationfollowing repeated baclofen administration may therefore underlie thecognitive deficits and learning impairments associated with baclofentreatment. Finally, abrupt discontinuation of intrathecal baclofenresults in severe withdrawal symptoms, including seizures (Ross, J. C.,et al. Neurocrit Care 2011; 14: 103-108). This indicates an underlyingchange in the physiological balance of GABA neurotransmitter and GABA-Breceptor after continued exogenous agonist stimulation. Similarly, theGABA-B knockout mouse exhibits epileptiform seizures, furtherunderscoring the importance of maintaining the normal, physiologicalGABA-B tone within the CNS. While the GABA-B receptor remains a validdrug target, the side effects and tolerance associated with baclofen hasled to the development of alternatives to classic orthosteric activationof the receptor.

To exploit the beneficial aspects of GABA-B stimulation, the disclosuredescribes positive allosteric receptor ligands for modulation of theGABA-B receptor. Positive allosteric modulators alter the receptorconformation and enhance the activity of the endogenous orthostericagonist, either by increasing the affinity or the efficacy of theorthosteric ligand at the receptor (Wang, L., et al. J Pharmacol ExpTher 2009; 331: 340-348). Because allosteric modulators rely on locallevels of endogenous ligand and have little or no activity of their own,they are thought to represent a safer and more subtle means of receptorregulation. The hypothesis is that GABA-B receptor allostericmodulators, and possibly allosteric agonists, will be effectivetherapeutic agents while minimizing the side effects caused by agonistactivation of the orthosteric GABA-B site. In addition to painindications (Anghinah, R., et al. Muscle Nerve 1994; 17(8): 958-959.Fromm G. H., et al. Ann. Neuro. 1984; 15: 240-244.), GABA-B modulatorscould also be used in the treatment of depression, spasticity (Bowery,N. G. Curr Opin Pharmacol 2006; 6; 37-433. Froestl, W. Expert Opin TherPat 2010; 20: 1007-1017. Ong, J., et al. CNS Drug Rev 2005; 11:317-334.)), fragile X syndrome (Lozano, R., et al. NeuropsychiatricDisease and Treatment 2014; 10: 1769-1779), Down's syndrome(Kleschevnikov, A. M., et al. Journal of Neuroscience 2012; 32(27):9217-9227), autism (Oblak, A. L., et al. Journal of Neurochemistry 2010;114(5): 1414-23), retinal ganglion cell degeneration (Hirano, A. A., etal. Journal of Comparative Neurology 2005; 488(1): 70-81),gastro-esophageal reflux disease (GERD) (Lacy, B. E., et al. Drugs ofthe Future 2010; 35(12): 987-992. Boeckxstaens, C. E. et al. CurrentOpinion in Pharmacology 2008; 8(6): 685-689. Lehmann, A., et al.Advances in Pharmacology 2010; 58: 287-313) smoking cessation (Vlachou,S., et al. Psychopharmacology 2011; 215(1): 117-128), addiction ofnarcotic agents (Spano, M. S., et al. Neuropharmacology 2007; 52(7):1555-62), emesis (Sanger, G. J., et al. Autonomic Neuroscience 2006;129(1-2): 3-16), cough (Bolser, D. C., et al. British Journal ofPharmacology 1993; 110(1): 491-495), overactive bladder (Taylor, M. C.,et al. British J. Urology 1979; 51: 504-505), anxiety (Krupitsky, E. M.,et al. Drug and Alcohol Dependence 1993; 33: 157-163. Cryan, J. F., etal. J Pharmacol Exp Ther 2004; 310: 952-963. Mombereau, C., et al.Neuropsychopharmacology 2004; 29: 1050-1062), migraine (Hering-Hanit,R., Cephalalgia 1999; 19(6): 589-91. Hering-Hanit, R., et al. Headache2000; 40(1): 48-51.), and tinnitus (Smith, P. F., et al. Frontiers inNeurology 2012; 3: 34). Positive allosteric modulators (PAMs) bind tofunctionally and topographically distinct allosteric sites on thereceptor and act at a distance from the orthosteric site to enhance theefficacy of the endogenous ligand. A single receptor may possessmultiple, discrete allosteric sites, each with a unique subset ofligands. Pure PAMs are devoid of activity on their own—they will onlyenhance the potency and/or efficacy of the endogenous agonist—thus theirpharmacological profile is spatially and temporally controlled by thenormal physiological interaction between the endogenous ligand and itsreceptor. This highlights a critical difference between PAMs andorthosteric agonists—PAMs avoid the maximum on/off at all receptors thatoccurs with classic orthosteric agonist stimulation. Because PAMs relyon endogenous agonist concentrations for activity, they promotefine-tuning of the GABA signal in a physiologically-relevant manner.Importantly, GABA-B PAMs do not cause receptor desensitization (Gjoni,T., et al. Neuropharmacology 2008; 55: 1293-1299), so the clinicaltolerance and side effects related to receptor desensitization that areobserved with baclofen are unlikely to occur. Finally, the majority ofGABA-B PAMs tested in the literature (Brusberg, M., et al.Neuropharmacology 2009; 56: 362-367. Froestl, W. Expert Opin Ther Pat2010; 20: 1007-1017. Koek, W., et al. J Pharmacol Exp Ther 2010; 335:163-17. Pin, J. P., et al. Curr Neuropharmacol 2007; 5, 195-201.) showgreatly enhanced brain penetrance as compared to baclofen and excellentefficacies in preliminary studies with minimum or no side effects. K.Ozadal et al., Bioorg. Med. Chem. (2012), 20(9), 2912-2922 describe theethyl esters of3-methyl-4-oxo-7-(phenylmethyl)-isoxazolo[4,5-d]pyridazine-5(4H)-aceticacid, of3-methyl-4-oxo-7-((4-methoxyphenyl)methyl)-isoxazolo[4,5-d]pyridazine-5(4H)-aceticacid and of3-methyl-4-oxo-7-((4-nitrophenyl)methyl)-isoxazolo[4,5-d]pyridazine-5(4H)-aceticacid as intermediates in the preparation of anti-inflammatoryisoxazolo[4,5-d]pyridazine-4(5H)-one compounds bearing either anamino-substituted 1,3,4-thiadiazole moiety or a 1,2,4-triazole-5-thionemoiety.

N. Cesari et al., J. Med. Chem. (2006), 49 (26), 7826-7835, describe3-methyl-4-oxo-7-phenyl-isoxazolo[4,5-d]pyridazine-5(4H)-propionic acidas an intermediate in the preparation ofarlypiperazinlylalkyl-substituted isoxazolo[4,5-d]pyridazine-4(5H)-ones,which are rally active antinociceptive agents.

V. Dal Piaz et al, Farmaco (2002), 57(2), 89-96 and Europ. J. Med. Chem.1998, 33(10), 789-797 describe, inter alia,3-methyl-7-phenyl-5-(phenylmethyl)-isoxazolo[4,5-d]pyridazin-4(5H)-one,3-methyl-7-phenyl-5-(prop-2-ynyl)-isoxazolo[4,5-d]pyridazin-4(5H)-one,3,5-dimethyl-7-phenyl-isoxazolo[4,5-d]pyridazin-4(5H)-one,5-ethyl-3-methyl-7-phenyl-isoxazolo[4,5-d]pyridazin-4(5H)-one and5-butyl-3-methyl-7-phenyl-isoxazolo[4,5-d]pyridazin-4(5H)-one asinhibitors of PDE III and PDE IV.

B. Chantegrel et al., J. Heterocycl. Chem., (1990), 27(4), 927-934describe the preparation of certain isocazolo[4,5-d]pyridzin-4(5H)ones,namely3-methyl-7-phenyl-5-(phenylmethyl)-isoxazolo[4,5-d]pyridazin-4(5H)-oneand 3, 7-dimethyl-5-(phenylmethyl)-isoxazolo[4,5-d]pyridazin-4(5H)-one.

H. M. Faidallah, Archives of Pharmaceutical Research (2013), 36(11),1354-1368, describe3,7-dimethyl-5-(2,2,2-trifluoroacetyl)-isoxazolo[4,5-d]pyridazoin-4(5H)-oneas an intermediate in the preparation of urea, thiourea or sulfonylureaderivatives of isoxazolo[4,5-d]pyridazin-4(5H)-ones having antibacterialproperties.

Apart from that, the ethyl ester of3-methyl-4-oxo-7-phenyl-isoxazolo[4,5-d]pyridazine-5(4H)-propionicacid[CAS 1027087-89-3] and3,5,7-trimethyl-isoxazolo[4,5-d]pyridazin-4(5H)-one [CAS 685542-42-1]can be found in databases.

These collective data emphasize the need for alternative therapeutics atthe GABA-B receptor, and highlight the unique ability of PAMs tostimulate the receptor without baclofen-like side effects.

SUMMARY

The invention is directed to substituted isoxazolopyridazinones andisothiazolopyridazinones having a structure of formula (I)

or a pharmaceutically acceptable salt or isotopically labelled formthereof, wherein:

X is O or S;

R¹ is selected from the group consisting of C₁-C₆alkyl, C₂-C₆alkenyl,C₂-C₆alkynyl, C₃-C₆cycloalkyl, and phenyl; wherein,

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or are substituted with one        or more, e.g. 1 or 2 substituents independently selected from        the group consisting of C₁-C₆alkoxy, fluoroC₁-C₆alkoxy, hydroxy,        and oxo;    -   C₃-C₆cycloalkyl is optionally substituted with one or more        substituents, e.g. from 1 to 6 substituents, which are        independently selected from the group consisting of C₁-C₆alkyl,        C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy,        hydroxy, and oxo;    -   phenyl is optionally substituted with one or more, e.g. 1, 2, 3,        4 or 5 substituents, selected from C₁-C₆alkyl, C₁-C₆alkoxy,        fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and halo;

R² is selected from the group consisting of C₁-C₆alkyl, C₂-C₆alkenyl,C₂-C₆alkynyl, and —(CR^(a)R^(b))_(n)-G¹; wherein,

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        more, e.g. 1 or 2, substituents independently selected from the        group consisting of C₁-C₆alkoxy, fluoroC₁-C₆alkoxy, hydroxy, and        oxo;    -   R^(a) and R^(b) are independently selected at each occurrence        from the group consisting of hydrogen, C₁-C₆alkyl,        fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and phenyl; wherein        -   phenyl is optionally substituted with one or more, e.g. 1,            2, 3, 4 or 5 substituents selected from C₁-C₆alkyl,            C₁-C₆alkoxy, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and halo;    -   n is 1, 2 or 3;    -   G¹ is selected from the group consisting of phenyl,        bicyclicaryl, monocyclic heteroaryl, and bicyclic heteroaryl;        wherein the phenyl, the bicyclicaryl, the monocyclic heteroaryl,        and the bicyclic heteroaryl are optionally substituted with 1,        2, 3 or 4 substituents independently selected from the group        consisting of C₁-C₆alkyl, C₁-C₆alkoxy, cyano, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, halo, and hydroxy;

R³ is selected from the group consisting of C₁-C₆alkyl, C₃-C₆cycloalkyl,phenyl, phenylC₁-C₆alkyl, bicyclicaryl, bicyclicarylC₁-C₆alkyl,monocyclic heteroarylC₁-C₆alkyl, monocyclic heteroaryl, and bicyclicheteroaryl; wherein

-   -   C₁-C₆alkyl is unsubstituted, partly or completely fluorinated        and/or substituted with one or more, e.g. 1 or 2, substituents        independently selected from the group consisting of C₁-C₆alkoxy,        fluoroC₁-C₆alkoxy, fluorine, hydroxy, and oxo;    -   C₃-C₆cycloalkyl is optionally substituted with one or more        substituents, e.g. with 1, 2, 3, 4,5 or 6 substituents,        independently selected from the group consisting of C₁-C₆alkyl,        fluoroC₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkoxy, fluorine,        hydroxy, and oxo; and    -   phenyl, phenyl of phenylC₁-C₆alkyl, bicyclicaryl, bicyclicaryl        of bicyclicarylC₁-C₆alkyl, monocyclic heteroaryl of monocyclic        heteroarylC₁-C₆alkyl, monocyclic heteroaryl and bicyclic        heteroaryl are optionally substituted with 1, 2, 3 or 4        substituents R^(Ar), which are independently selected from the        group consisting of C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl,        halogen, cyano, —OR^(1a), —OC(O)R^(1a), —OC(O)N(R^(d))(R^(3a)),        —SR^(1a), —S(O)₂R^(2a), —S(O)₂N(R^(d))(R^(3a)), —C(O)R^(1a),        —C(O)OR^(1a), —C(O)N(R^(d))(R^(3a)), —N(R^(d))(R^(3a)),        —N(R^(c))C(O)R^(1a), —N(R^(c))S(O)₂R^(2a),        —N(R^(c))C(O)O(R^(1a)), —N(R^(c))C(O)N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—OR^(1a), —(CR^(4a)R^(5a))_(m)—OC(O)R^(1a),        —(CR^(4a)R^(5a))_(m)—OC(O)N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—SR^(1a), —(CR^(4a)R^(5a))_(m)—S(O)₂R^(2a),        —(CR^(4a)R^(5a))_(m)—S(O)₂N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—C(O)R^(1a),        —(CR^(4a)R^(5a))_(m)—C(O)OR^(1a),        —(CR^(4a)R^(5a))_(m)—C(O)N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)R^(1a),        —(CR^(4a)R^(5a))_(m)—N(R^(c))S(O)₂R^(2a),        —(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)O(R^(1a)),        —(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)N(R^(d))(R^(3a)),        cyanoC₁-C₆-alkyl and fluoroC₁-C₆-alkyl;        -   m is 1, 2, 3, or 4;        -   R^(c) and R^(d), at each occurrence, are each independently            hydrogen, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl;    -   R^(1a) and R^(3a), at each occurrence, are each independently        hydrogen, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl;    -   R^(d) and R^(3a), if present as a group N(R^(d))(R^(3a)), such        as in substituents —C(O)N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—C(O)N(R^(d))(R^(3a)),        —S(O)₂N(R^(d))(R^(3a)), —N(R^(c))C(O)N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—S(O)₂N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)N(R^(d))(R^(3a)),        —(CR^(4a)R^(5a))_(m)—N(R^(d))(R^(3a)), or —N(R^(d))(R^(3a)), may        together with the nitrogen atom of N(R^(d))(R^(3a)) also form an        N-bound saturated, 3 to 8 membered heterocycle, which in        addition to the nitrogen atom may have 1 or 2 further        heteroatoms as ring members, which are selected from O, S and N;        -   R^(c) and R^(1a), if present as a group —N(R^(c))C(O)R^(1a),            may together with the atoms of said moiety form an N-bound            saturated 3 to 8 membered heterocycle, which has an oxo            group in 2-position and which in addition to the nitrogen            atom may have 1 or 2 further heteroatoms as ring members,            which are selected from O, S and N; and        -   R^(2a), at each occurrence, is independently C₁-C₆alkyl, or            fluoroC₁-C₆-alkyl; and        -   R^(4a) and R^(5a), at each occurrence, are each            independently hydrogen, fluorine, C₁-C₆alkyl, or            fluoroC₁-C₆-alkyl.

The following groups of compounds of the formula (I) are not part of theinvention:

Compounds of formula (I), where X is O, R1 is methyl, R2 is methyl,ethyl, n-butyl, unsubstituted benzyl, prop-2-ynyl,2-(ethoxycarbonyl)ethyl or 2-carboxyethyl and R3 is unsubstitutedphenyl;

Compounds of formula (I), where X is O, R1 is methyl, R2 is methyl,2,2,2-trifluoroacetyl or unsubstituted benzyl, and R3 is methyl;

Compounds of formula (I), where X is O, R1 is methyl, R2 isethoxycarbonylmethyl and R3 is unsubstituted benzyl, or 4-methoxybenzyl.

Another aspect of the invention relates to pharmaceutical compositionscomprising at least one compound of the invention, i.e. a compound ofthe formula (I), a pharmaceutically acceptable salt or isotopicallylabelled form thereof. In particular, the invention relates to apharmaceutically composition comprising a therapeutically effectiveamount of a compound of the invention, i.e. a compound of the formula(I), a pharmaceutically acceptable salt or isotopically labelled formthereof in combination with a pharmaceutically acceptable carrier,diluent or excipient. Such compositions can be administered inaccordance with a method or use of the invention, typically as part of atherapeutic regimen for treatment or prevention of conditions anddisorders related to γ-aminobutyric acid receptor B (GABA-B) activity.

Yet another aspect of the invention relates to a method of enhancing theactivity of the endogenous orthosteric agonist by altering the GABA-Breceptor conformation by treatment at an allosteric binding site with apositive allosteric modulator.

The invention also relates to the compounds of the invention, apharmaceutically acceptable salt or isotopically labelled form thereoffor use in therapy, in particular for use in the treatment of acondition or disorder modulated by the γ-aminobutyric acid B (GABA-B)receptor in a mammal.

The invention also relates to the use of a compound of the invention, apharmaceutically acceptable salt or isotopically labelled form thereoffor the preparation of a medicament, in particular for the preparationof a medicament for the treatment of a condition or disorder modulatedby the γ-aminobutyric acid B (GABA-B) receptor in a mammal.

Conditions and disorders related to γ-aminobutyric acid receptor B(GABA-B) activity include but are not limited to pain, substance abuse(especially in alcohol dependence), spasticity, fragile X syndrome,Down's syndrome, autism, retinal ganglion cell degeneration,gastro-esophageal reflux disease (GERD), smoking cessation, addiction ofnarcotic agents, emesis, cough, overactive bladder, anxiety, migraineand tinnitus, preferably in mammals. Accordingly, the compounds andcompositions of the invention are useful as a medicament for treating orpreventing γ-aminobutyric acid receptor B modulated diseases.

The compounds, compositions comprising the compounds, methods for makingthe compounds, and methods for treating or preventing conditions anddisorders by administering the compounds are further described herein.

In a particular aspect, the compounds of the invention are provided foruse in the treatment of pain, substance abuse (especially in alcoholdependence), and spasticity.

In an alternative embodiment, certain of the compounds of the inventionhave a positive allosteric modulator activity.

These and other objects of the invention are described in the followingparagraphs. These objects should not be deemed to narrow the scope ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

Described herein are compounds of formula (I)

wherein R¹, R², R³, and X are defined above in the Summary and below inthe Detailed Description. Further, compositions comprising suchcompounds and methods for treating conditions and disorders using suchcompounds and compositions are also described.

Compounds described herein may contain one or more variable(s) thatoccur more than one time in any substituent or in the formulae herein.Definition of a variable on each occurrence is independent of itsdefinition at another occurrence. Further, combinations of substituentsare permissible only if such combinations result in stable compounds.Stable compounds are compounds which can be isolated from a reactionmixture.

Definitions of Terms

It is noted that, as used in this specification and the intended claims,the singular form “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“a compound” includes a single compound as well as one or more of thesame or different compounds, reference to “optionally a pharmaceuticallyacceptable carrier” refers to a single optional pharmaceuticallyacceptable carrier as well as one or more pharmaceutically acceptablecarriers, and the like.

Certain terms as used in the specification are intended to refer to thefollowing definitions, as detailed below.

The term “alkenyl” as used herein, means a straight or branchedhydrocarbon chain containing from 2 to 10 carbons and containing atleast one carbon-carbon double bond. Representative examples of alkenylinclude, but are not limited to, ethenyl, 2-propenyl,2-methyl-2-propenyl, 3-butenyl, 4-pentenyl, 5-hexenyl, 2-heptenyl,2-methyl-1-heptenyl, and 3-decenyl.

The term “alkenylene” means a divalent group derived from a straight orbranched chain hydrocarbon of from 2 to 10 carbon atoms containing atleast one double bond. Representative examples of alkenylene include,but are not limited to, —CH═CH—, —CH═CH2CH2-, and —CH═C(CH3)CH2-.

The term “alkoxy” as used herein means an alkyl group, as definedherein, appended to the parent molecular moiety through an oxygen atom.Representative examples of alkoxy include, but are not limited to,methoxy, ethoxy, propoxy, 2-propoxy, butoxy, tent-butoxy, pentyloxy, andhexyloxy.

The term “alkyl” as used herein, and likewise the term “alkyl” inalkylcarbonyl, alkylcarbonylamino, alkylsulfonyl and alkylsulfonylamino,means a straight or branched, saturated hydrocarbon chain containingfrom 1 to 10 carbon atoms. The term “lower alkyl” or “C₁-C₆alkyl” meansa straight or branched chain hydrocarbon containing from 1 to 6 carbonatoms. The term “C₁-C₃alkyl” means a straight or branched chainhydrocarbon containing from 1 to 3 carbon atoms. Representative examplesof alkyl include, but are not limited to, methyl, ethyl, n-propyl,iso-propyl, n-butyl, se c -butyl, iso-butyl, tent-butyl, n-pentyl,isopentyl, neopentyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl,2,3-dimethylpentyl, n-heptyl, n-octyl, n-nonyl, and n-decyl.

The term “alkylene” denotes a divalent group derived from a straight orbranched chain hydrocarbon containing from 1 to 10 carbon atoms.Representative examples of alkylene include, but are not limited to,—CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂—.

The term “alkynyl” as used herein, means a straight or branched chainhydrocarbon group containing from 2 to 10 carbon atoms and containing atleast one carbon-carbon triple bond. Representative examples of alkynylinclude, but are not limited to, acetylenyl, 1-propynyl, 2-propynyl,3-butynyl, 2-pentynyl, and 1-butynyl.

In the context of alkyl, alkenyl and alkynyl the term “partly orcompletely fluorinated” means that at least one, e.g. 1, 2, 3, 4,5, 6,7, 8 or 9 or all of the hydrogen atoms of alkyl, alkenyl or alkynyl hasbeen replaced by fluorine atoms.

The term “aryl” as used herein, means phenyl or a bicyclicaryl. Thebicyclicaryl is naphthyl, or a phenyl fused to a monocyclic cycloalkyl,or a phenyl fused to a monocyclic cycloalkenyl. Representative examplesof the aryl groups include, but are not limited to, dihydroindenyl,indenyl, naphthyl, dihydronaphthalenyl, and tetrahydronaphthalenyl. Thebicyclicaryl is attached to the parent molecular moiety through anycarbon atom contained within the bicyclic ring system. The aryl groupsof the present invention can be unsubstituted or substituted.

The term “alkoxyalkyl” as used herein, means an alkoxy group, as definedherein, appended to the parent molecular moiety through an alkylenegroup, as defined herein. Representative examples of alkoxyalkylinclude, but are not limited to, methoxymethyl, ethoxymethyl,2-methoxyethyl, 2-ethoxyethyl, 2-methoxypropyl, 2-ethoxypropyl,3-methoxypropyl and 3-ethoxypropyl.

The term “arylalkyl” as used herein, means an aryl group, as definedherein, appended to the parent molecular moiety through an alkylenegroup, as defined herein. Representative examples of arylalkyl include,but are not limited to, benzyl, 1-phenylethyl, 2-phenylethyl,3-phenylpropyl, and 2-naphth-2-ylethyl.

The term “carbonyl” as used herein means a —C(═O)— group.

The term “carboxy” as used herein means a —CO₂H group.

The term “cyano” as used herein, means a —CN group.

The terms “amido” and “carbamoyl”, as used herein means a —C(O)NH2group.

The term “amino” as used herein means an —NH₂ group.

The term “cycloalkyl” or “cycloalkane” as used herein, means amonocyclic, a bicyclic, a tricyclic, or a spirocyclic cycloalkyl. Themonocyclic cycloalkyl is a carbocyclic ring system containing three toeight carbon atoms, zero heteroatoms and zero double bonds. Examples ofmonocyclic ring systems include cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, and cyclooctyl. The bicyclic cycloalkyl is amonocyclic cycloalkyl fused to a monocyclic cycloalkyl ring, or abridged monocyclic ring system in which two non-adjacent carbon atoms ofthe monocyclic ring are linked by an alkylene bridge containing one,two, three, or four carbon atoms. Representative examples of bicyclicring systems include, but are not limited to, bicyclo[3.1.1]heptane,bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, bicyclo[3.2.2]nonane,bicyclo[3.3.1]nonane, and bicyclo[4.2.1]nonane. Tricyclic cycloalkylsare exemplified by a bicyclic cycloalkyl fused to a monocycliccycloalkyl, or a bicyclic cycloalkyl in which two non-adjacent carbonatoms of the ring systems are linked by an alkylene bridge of 1, 2, 3,or 4 carbon atoms. Representative examples of tricyclic-ring systemsinclude, but are not limited to, tricyclo[3.3.1.0^(3,7)]nonane(octahydro-2,5-methanopentalene or noradamantane), andtricyclo[3.3.1.1^(3,7)]decane (adamantane). The monocyclic, bicyclic,and tricyclic cycloalkyls can be unsubstituted or substituted, and areattached to the parent molecular moiety through any substitutable atomcontained within the ring system. Spirocyclic cycloalkyl is exemplifiedby a monocyclic or a bicyclic cycloalkyl, wherein two of thesubstituents on the same carbon atom of the ring, together with saidcarbon atom, form a 4-, 5-, or 6-membered monocyclic cycloalkyl. Anexample of a spirocyclic cycloalkyl is spiro[2.5]octane. The spirocycliccycloalkyl groups of the present invention can be appended to the parentmolecular moiety through any substitutable carbon atom of the groups.

The term “fluoroalkyl” as used herein, means an alkyl group, as definedherein, in which one, two, three, four, five, six, seven or eighthydrogen atoms are replaced by fluorine. Representative examples offluoroalkyl include, but are not limited to, fluoromethyl,2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, trifluoromethyl,difluoromethyl, pentafluoroethyl, 1,1,2-trifluoroisopropyl, andtrifluoropropyl such as 3,3,3-trifluoropropyl.

The term “halo” or “halogen” as used herein, means Cl, Br, I, or F.

The term “haloalkyl” as used herein, means an alkyl group, as definedherein, in which one, two, three, four, five, six, seven or eighthydrogen atoms are replaced by halogen, in particular by fluorine.Representative examples of haloalkyl include, but are not limited to,chloromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, trifluoromethyl,difluoromethyl, pentafluoroethyl, 2-chloro-3-fluoropentyl, andtrifluoropropyl such as 3,3,3-trifluoropropyl.

The term “heteroaryl” as used herein, means a heterocyclicaromaticradical and includes monocyclic heteroaryl and bicyclic heteroaryl. Themonocyclic heteroaryl is a five- or six-membered ring. The five-memberedring contains two double bonds. The five-membered ring may contain oneheteroatom selected from O or S; or one, two, three, or four nitrogenatoms and optionally one oxygen or sulfur atom. The six-membered ringcontains three double bonds and one, two, three or four nitrogen atoms.Representative examples of monocyclic heteroaryl include, but are notlimited to, furanyl, imidazolyl, isoxazolyl, isothiazolyl, oxadiazolyl,1,3-oxazolyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyrazolyl,pyrrolyl, tetrazolyl, thiadiazolyl, 1,3-thiazolyl, thienyl, triazolyl,and triazinyl. The bicyclic heteroaryl consists of a monocyclicheteroaryl fused to a phenyl, or a monocyclic heteroaryl fused to amonocyclic cycloalkyl, or a monocyclic heteroaryl fused to a monocycliccycloalkenyl, or a monocyclic heteroaryl fused to a monocyclicheteroaryl, or a monocyclic heteroaryl fused to a monocyclicheterocycle. Representative examples of bicyclic heteroaryl groupsinclude, but are not limited to, benzofuranyl, benzothienyl,benzoxazolyl, benzimidazolyl, benzoxadiazolyl,6,7-dihydro-1,3-benzothiazolyl, imidazo[1,2-a]pyridinyl, indazolyl,indolyl, isoindolyl, isoquinolinyl, naphthyridinyl, pyridoimidazolyl,quinolinyl, thiazolo[5,4-b]pyridin-2-yl, thiazolo[5,4-d]pyrimidin-2-yl,and 5,6,7,8-tetrahydroquinolin-5-yl. The monocyclic and bicyclicheteroaryl groups of the present invention can be substituted orunsubstituted and are connected to the parent molecular moiety throughany carbon atom or any nitrogen atom contained within the ring systems.

The term “heteroarylalkyl”, as used herein, refers to refers to aheteroaryl group attached to the parent molecular moiety through analkyl group.

The term “heterocycle” or “heterocyclic” as used herein, means anon-aromatic heterocyclic radical and includes a monocyclic heterocycle,a bicyclic heterocycle, a tricyclic heterocycle, or a spirocyclicheterocycle. If not stated otherwise, the heterocyclic radical issaturated or has one or two non-conjugated endocyclic double bounds,e.g. a C═N or C═C double bond. The monocyclic heterocycle is a three-,four-, five-, six-, seven-, or eight-membered ring containing at leastone heteroatom independently selected from the group consisting of O, N,and S. The three- or four-membered ring contains zero or one doublebond, and one heteroatom selected from the group consisting of O, N, andS. The five-membered ring contains zero or one double bond and one, twoor three heteroatoms selected from the group consisting of O, N and S.The six-membered ring contains zero, one or two double bonds and one,two, or three heteroatoms selected from the group consisting of O, N,and S. The seven- and eight-membered rings contains zero, one, two, orthree double bonds and one, two, or three heteroatoms selected from thegroup consisting of O, N, and S. Representative examples of monocyclicheterocycles include, but are not limited to, azetidinyl, azepanyl,aziridinyl, diazepanyl, 1,3-dioxanyl, 1,3-dioxolanyl, 1,3-dithiolanyl,1,3-dithianyl, imidazolinyl, imidazolidinyl, isothiazolinyl,isothiazolidinyl, isoxazolinyl, isoxazolidinyl, morpholinyl,oxadiazolinyl, oxadiazolidinyl, oxazolinyl, oxazolidinyl, oxetanyl,piperazinyl, piperidinyl, pyranyl, pyrazolinyl, pyrazolidinyl,pyrrolinyl, pyrrolidinyl, tetrahydrofuranyl, tetrahydropyranyl,tetrahydropyridinyl, tetrahydrothienyl, thiadiazolinyl,thiadiazolidinyl, 1,2-thiazinanyl, 1,3-thiazinanyl, thiazolinyl,thiazolidinyl, thiomorpholinyl, 1,1-dioxidothiomorpholinyl(thiomorpholine sulfone), thiopyranyl, and trithianyl. The bicyclicheterocycle is a monocyclic heterocycle fused to a phenyl group, or amonocyclic heterocycle fused to a monocyclic cycloalkyl, or a monocyclicheterocycle fused to a monocyclic cycloalkenyl, or a monocyclicheterocycle fused to a monocyclic heterocycle, or a bridged monocyclicheterocycle ring system in which two non-adjacent atoms of the ring arelinked by an alkylene bridge of 1, 2, 3, or 4 carbon atoms, or analkenylene bridge of two, three, or four carbon atoms. Representativeexamples of bicyclic heterocycles include, but are not limited to,benzopyranyl, benzothiopyranyl, chromanyl, 2,3-dihydrobenzofuranyl,2,3-dihydrobenzothienyl, 2,3-dihydroisoquinoline,azabicyclo[2.2.1]heptyl (including 2-azabicyclo[2.2.1]hept-2-yl),2,3-dihydro-1H-indolyl, isoindolinyl, octahydrocyclopenta[c]pyrrolyl,octahydropyrrolopyridinyl, and tetrahydroisoquinolinyl. Tricyclicheterocycles are exemplified by a bicyclic heterocycle fused to a phenylgroup, or a bicyclic heterocycle fused to a monocyclic cycloalkyl, or abicyclic heterocycle fused to a monocyclic cycloalkenyl, or a bicyclicheterocycle fused to a monocyclic heterocycle, or a bicyclic heterocyclein which two non-adjacent atoms of the bicyclic ring are linked by analkylene bridge of 1, 2, 3, or 4 carbon atoms, or an alkenylene bridgeof two, three, or four carbon atoms. Examples of tricyclic heterocyclesinclude, but not limited to, octahydro-2,5-epoxypentalene,hexahydro-2H-2,5-methanocyclopenta[b]furan,hexahydro-1H-1,4-methanocyclopenta[c]furan, aza-adamantane(1-azatricyclo[3.3.1.1^(3,7)]decane), oxa-adamantane(2-oxatricyclo[3.3.1.1^(3,7)]decane), andoctahydro-1H-4,7-epiminoisoindole. The spirocyclic heterocycles areexemplified by a monocyclic heterocycle as defined herein wherein onecarbon atom of the monocyclic heterocycle is bridged by two ends of analkylene chain. In the spirocyclic heterocycle, one or more carbon atomsin the bridging alkylene chain may be replaced with a heteroatom.Examples of spirocyclic heterocycles include, but are not limited to,4,7-diazaspiro[2.5]octane, 2-oxa-6-azaspiro[3.3]heptane,2,6-diazaspiro[3.3]heptane, 2-oxa-5,8-diazaspiro[3.5]nonane,2,7-diazaspiro[3.5]nonane, 1,4-dioxa-8-azaspiro[4.5]decane,1,6-diazaspiro[3.3]heptane, 1-azaspiro[4.4]nonane,7-azaspiro[3.5]nonane, 1,4-dioxa-7-azaspiro[4.4]nonane,5,8-diazaspiro[3.5]nonane, 5,8-dioxa-2-azaspiro[3.4]octane,2-oxa-6-azaspiro[3.4]octane, 6-oxa-1-azaspiro[3.3]heptane,6-oxa-2-azaspiro[3.4]octane, 6-oxa-2-azaspiro[3.5]nonane, and7-oxa-2-azaspiro[3.5]nonane. The monocyclic, bicyclic, tricyclic, andspirocyclic heterocycles are connected to the parent molecular moietythrough any carbon atom or any nitrogen atom contained within the rings,and can be unsubstituted or substituted.

The term “heterocycloalkyl”, as used herein, refers to refers to aheterocycle group attached to the parent molecular moiety through analkyl group.

The term “heterocyclecarbonyl” refers to a heterocycle, as definedherein, appended to the parent molecular moiety through a carbonylgroup, as defined herein. Representative examples of heterocyclocarbonylinclude, but are not limited to, piperidine-1-carbonyl,morpholine-4-carbonyl, and pyrrolidine-1-carbonyl.

The term “heteroatom” as used herein, means a nitrogen, oxygen, orsulfur atom.

The term “hydroxyl” or “hydroxy” as used herein, means an —OH group.

The term “oxo” as used herein means (═O).

If, for example, alkyl, alkenyl or alkynyl are substituted with bothhydroxy and oxo, hydroxy and oxo may be bound to the same carbon atomthus forming a carboxy group.

If, for example, alkyl, alkenyl or alkynyl are substituted with bothalkoxy and oxo, alkoxy and oxo may be bound to the same carbon atom thusforming an alkoxycarbonyl group.

In some instances, the number of carbon atoms in a hydrocarbylsubstituent (e.g., alkyl, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkoxy, and haloalkoxy, etc.) is indicated by the prefix “C_(x)-C_(y)”,wherein x is the minimum and y is the maximum number of carbon atoms inthe substituent. Thus, for example, “C₁-C₆alkyl” refers to an alkylsubstituent containing from 1 to 6 carbon atoms. Illustrating further,C₃-C₆cycloalkyl means a saturated hydrocarbyl ring containing from 3 to6 carbon ring atoms.

As used herein, the term “radiolabel” or “isotopically labeled form”refers to a compound of the invention in which at least one of the atomsis a radioactive atom or radioactive isotope, wherein the radioactiveatom or isotope spontaneously emits gamma rays or energetic particles,for example alpha particles or beta particles, or positrons. Examples ofsuch radioactive atoms include, but are not limited to, ³H (tritium),¹⁴C, ¹¹C, ¹⁵O, ¹⁸F, ³⁵S, ¹²³I, and ¹²⁵I.

If a moiety is described as “substituted”, a non-hydrogen radical is inthe place of hydrogen radical of any substitutable atom of the moiety.Thus, for example, a substituted heterocycle moiety is a heterocyclemoiety in which at least one non-hydrogen radical is in the place of ahydrogen radical on the heterocycle. It should be recognized that ifthere are more than one substitution on a moiety, each non-hydrogenradical may be identical or different (unless otherwise stated).

If a moiety is described as being “optionally substituted,” the moietymay be either (1) not substituted or (2) substituted. If a moiety isdescribed as being optionally substituted with up to a particular numberof non-hydrogen radicals, that moiety may be either (1) not substituted;or (2) substituted by up to that particular number of non-hydrogenradicals or by up to the maximum number of substitutable positions onthe moiety, whichever is less. Thus, for example, if a moiety isdescribed as a heteroaryl optionally substituted with up to 3non-hydrogen radicals, then any heteroaryl with less than 3substitutable positions would be optionally substituted by up to only asmany non-hydrogen radicals as the heteroaryl has substitutablepositions. To illustrate, tetrazolyl (which has only one substitutableposition) would be optionally substituted with up to one non-hydrogenradical. To illustrate further, if an amino nitrogen is described asbeing optionally substituted with up to 2 non-hydrogen radicals, then aprimary amino nitrogen will be optionally substituted with up to 2non-hydrogen radicals, whereas a secondary amino nitrogen will beoptionally substituted with up to only 1 non-hydrogen radical.

The terms “treat”, “treating”, and “treatment” refer to a method ofalleviating or abrogating a disease and/or its attendant symptoms.

The terms “prevent”, “preventing”, and “prevention” refer to a method ofpreventing the onset of a disease and/or its attendant symptoms orbarring a subject from acquiring a disease. As used herein, “prevent”,“preventing” and “prevention” also include delaying the onset of adisease and/or its attendant symptoms and reducing a subject's risk ofacquiring a disease.

The phrase “therapeutically effective amount” means an amount of acompound, or a pharmaceutically acceptable salt thereof, sufficient toprevent the development of or to alleviate to some extent one or more ofthe symptoms of the condition or disorder being treated whenadministered alone or in conjunction with another therapeutic agent ortreatment in a particular subject or subject population. For example ina human or other mammal, a therapeutically effective amount can bedetermined experimentally in a laboratory or clinical setting, or may bethe amount required by the guidelines of the United States Food and DrugAdministration, or equivalent foreign agency, for the particular diseaseand subject being treated.

The term “subject” is defined herein to refer to animals such asmammals, including, but not limited to, primates (e.g., humans), cows,sheep, goats, pigs, horses, dogs, cats, rabbits, rats, mice and thelike. In preferred embodiments, the subject is a human.

Compounds of the Invention

Compounds of the invention can have the formula (I) as described in theSummary. Particular values of variable groups in compounds of formula(I) are as follows. Such values can be used where appropriate with anyof the other values, definitions, claims or embodiments definedhereinbefore or hereinafter.

Irrespective of its occurrence, R¹ is as defined above or selected fromthe group consisting of C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl andC₃-C₆cycloalkyl; wherein:

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine.

Irrespective of its occurrence, R¹ may also be selected from the groupconsisting of C₁-C₆alkyl, fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl andcyclopropyl, wherein cyclopropyl is unsubstituted or substituted with 1or 2 substituents independently selected from the group consisting ofC₁-C₃alkyl, fluorine, and fluoroC₁-C₃alkyl.

Irrespective of its occurrence, R¹ may also be selected from the groupconsisting of C₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl and cyclopropyl,wherein cyclopropyl is unsubstituted or substituted with 1 or 2substituents independently selected from the group consisting of methyl,ethyl, fluorine, and fluoroC₁-C₂alkyl.

Irrespective of its occurrence, R¹ may also be phenyl, which isunsubstituted or substituted with 1, 2, 3 or 4 substituents or with 1 or2 substituents, where the substituents are selected from the groupconsisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl,fluoroC₁-C₆alkoxy, and halo, and where the substituents are inparticular selected from the group consisting of C₁-C₃alkyl,C₁-C₃alkoxy, fluoroC₁-C₂alkyl, fluoroC₁-C₂alkoxy, fluorine or chlorine.

Examples of R¹ include methyl, ethyl, isopropyl, n-propyl, cyclopropyl,methoxymethyl, phenyl which is unsubstituted or substituted by halo.

According to a first group of embodiments, R² is selected from the groupconsisting of C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo or where C₁-C₆alkyl,        C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular unsubstituted        or partly or completely fluorinated.

According to a subgroup of the first group of embodiments, R² isC₁-C₆alkyl, which is unsubstituted, partly or completely fluorinatedand/or substituted with one or two substituents independently selectedfrom the group consisting of C₁-C₆alkoxy, hydroxy, and oxo or whereC₁-C₆alkyl is in particular unsubstituted or partly or completelyfluorinated.

According to a further subgroup of the first group of embodiments, R² isC₁-C₆alkyl or fluoroC₁-C₆alkyl.

Examples of such radicals R² of this first group of embodiments includebut are not limited to methyl, ethyl, n-propyl, n-butyl, isobutyl,2-methylbutyl and 3-methylbutyl.

In the first group and in the subgroups of the first group ofembodiments, R¹ is as defined above or selected from the groupconsisting of C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl andC₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine.

In the first group and in the subgroups of the first group ofembodiments, R¹ may also be selected from the group consisting ofC₁-C₆alkyl, fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl,wherein cyclopropyl is unsubstituted or substituted with 1 or 2substituents independently selected from the group consisting ofC₁-C₃alkyl, fluorine, and fluoroC₁-C₃alkyl.

In the first group and in the subgroups of the first group ofembodiments, R¹ may also be selected from the group consisting ofC₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of methyl, ethyl,fluorine, and fluoroC₁-C₂alkyl.

In the first group and in the subgroups of the first group ofembodiments, R¹ may also be phenyl, which is unsubstituted orsubstituted with 1, 2, 3 or 4 substituents or with 1 or 2 substituents,where the substituents are selected from the group consisting ofC₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and halo,and where the substituents are in particular selected from the groupconsisting of C₁-C₃alkyl, C₁-C₃alkoxy, fluoroC₁-C₂alkyl,fluoroC₁-C₂alkoxy, fluorine or chlorine.

According to a second group of embodiments, R² is —(CR^(a)R^(b))_(n)-G¹,wherein n, R^(a), R^(b) and G¹ are as defined above, or wherein n is 1or 2 or wherein n is 1.

If G¹ is a phenyl radical, phenyl is in particular substituted with 1,2, 3 or 4 substituents as defined above.

A skilled person will readily appreciate that for n being 2 or 3 themoieties CR^(a)R^(b) can be identical or different.

According to a first subgroup of the second group of embodiments, R² is—(CR^(a)R^(b))_(n)-G¹, wherein n, R^(a) and R^(b) are as defined aboveand wherein G¹ is selected from the group consisting of phenyl andmonocyclic heteroaryl, in particular phenyl and 6 membered monocyclichetaryl, such as 2, 3 or 4 pyridyl;

wherein the phenyl and the monocyclic heteroaryl of G¹ are unsubstitutedor substituted with 1, 2, 3 or 4 substituents, in particular with 1 or 2substituents, which are independently selected from the group consistingof C₁-C₆alkyl, C₁-C₆alkoxy, cyano, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy,halo, and hydroxy.

According to a second subgroup of the second group of embodiments, R² is—(CR^(a)R^(b))_(n)-G¹, wherein n, R^(a) and R^(b) are as defined aboveand wherein G¹ is phenyl, which is unsubstituted or in particularsubstituted with 1, 2, 3 or 4 substituents, where the substituents areindependently selected from the group consisting of C₁-C₆alkyl,C₁-C₆alkoxy, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, halo, and hydroxyl andin particular from the group consisting of C₁-C₃alkyl, C₁-C₃alkoxy,fluoroC₁-C₃alkyl, fluorine and chlorine.

According to a third subgroup of the second group of embodiments, R² is—(CR^(a)R^(b))_(n)-G¹, wherein n, R^(a) and R^(b) are as defined aboveand wherein G¹ is phenyl, which is substituted with 1 or 2 substituentsas defined above, where the substituents are independently selected fromthe group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl,fluoroC₁-C₆alkoxy, halo, and hydroxyl and in particular from the groupconsisting of C₁-C₃alkyl, C₁-C₃alkoxy, fluoroC₁-C₃alkyl, fluorine andchlorine.

In the second group of embodiments and in the first, second and thirdsubgroup of embodiments, R^(a) and R^(b) are as defined above,

or R^(a) and R^(b) are independently selected at each occurrence fromthe group consisting of hydrogen, C₁-C₆alkyl and phenyl, wherein phenylis unsubstituted or substituted with 1, 2 or 3 substituents selectedfrom the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl,fluoroC₁-C₆alkoxy, and halo;

or R^(a) and R^(b) are independently selected at each occurrence fromthe group consisting of hydrogen, C₁-C₃alkyl and phenyl, wherein phenylis unsubstituted or substituted with 1, 2 or 3 substituents selectedfrom the group consisting of C₁-C₃alkyl, fluoroC₁-C₃alkyl, C₁-C₃alkoxy,fluorine and chlorine.

or R^(a) and R^(b) are independently selected at each occurrence fromthe group consisting of hydrogen, methyl and phenyl, wherein phenyl isunsubstituted or substituted with 1 or 2 substituents selected from thegroup consisting of methyl, trifluoromethyl, methoxy, fluorine andchlorine.

In particular, either one or both of the radicals R^(a) and R^(b) ofeach group CR^(a)R^(b) is/are hydrogen.

In a fourth subgroup of the second group of embodiments, the moiety—(CR^(a)R^(b))_(n)— is CH₂, CH₂CH₂, CH(CH₃) or CH(phenyl), where phenylis unsubstituted or carries 1 substituent as defined above or asubstituent selected from the group consisting of C₁-C₃alkyl,C₁-C₃alkoxy, fluorine and chlorine. In this particular subgroup of thesecond embodiments, and G1 is as above.

In fifth subgroup of the second group of embodiments, the moiety—(CR^(a)R^(b))_(n)— is CH₂, CH₂CH₂, CH(CH₃) or CH(phenyl), where phenylis unsubstituted or carries 1 substituent as defined above or asubstituent selected from the group consisting of C₁-C₃alkyl,C₁-C₃alkoxy, fluorine and chlorine and G1 is as defined in the first,second or third subgroup of the second group of embodiments.

In a sixth subgroup of the second group of embodiments the moiety—(CR^(a)R^(b))_(n)— is CH(CH₃).

In a seventh subgroup of the second group of embodiments the moiety—(CR^(a)R^(b))_(n)— is CH(CH₃), which has predominately R-configuration.Predominately R-configuration means that the molar ratio of theR-enantiomer to the S-enantiomer is >1:1, in particular >3:1, moreparticularly >4:1 and especially >9:1.

In an eighth subgroup of the second group of embodiments the moiety—(CR^(a)R^(b))_(n)— is CH(CH₃), which has predominately R-configurationand G1 is as defined in the first, second or third subgroup ofembodiments.

Examples of such radicals R² of this second group of embodiments includebut are not limited to 4-chlorphenylmethyl,3-(trifluoromethyl)phenylmethyl, 4-(trifluoromethyl)phenylmethyl,4-methoxy-3-(trifluoromethyl)phenylmethyl,2-fluoro-5-(trifluoromethyl)phenylmethyl, 5-chloro-2-fluorophenylmethyl,4-chloro-2-fluorophenylmethyl, 4-chlorophenylphenylmethyl,2,4-difluorophenylmethyl, 4-fluoro-3-(trifluoromethyl)phenylmethyl,4-chloro-3-(trifluoromethyl)phenylmethyl, 2-fluorophenylmethyl,4-fluorophenylmethyl, (1RS)-1-(4-chlorphenyl)ethyl,(1R)-1-(4-chlorphenyl)ethyl, (1S)-1-(4-chlorphenyl)ethyl,2-(4-chlorphenyl)ethyl, (1RS)-1-(4-(trifluoromethyl)phenyl)ethyl,(1R)-1-(4-(trifluoromethyl)phenyl)ethyl,(1S)-1-(4-(trifluoromethyl)phenyl)ethyl, and 4-pyridylmethyl.

In the second group of embodiments and also in the first, second, third,fourth, fifth, sixth, seventh and eighth subgroups of the second groupof embodiments, R¹ is as defined above or selected from the groupconsisting of C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl andC₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine.

In the second group of embodiments and also in the first, second, third,fourth, fifth, sixth, seventh and eighth subgroups of the second groupof embodiments, R¹ may also be selected from the group consisting ofC₁-C₆alkyl, fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl,wherein cyclopropyl is unsubstituted or substituted with 1 or 2substituents independently selected from the group consisting ofC₁-C₃alkyl, fluorine, and fluoroC₁-C₃alkyl.

In the second group of embodiments and also in the first, second, third,fourth, fifth, sixth, seventh and eighth subgroups of the second groupof embodiments, R¹ may also be selected from the group consisting ofC₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of methyl, ethyl,fluorine, and fluoroC₁-C₂alkyl.

In the second group of embodiments and also in the first, second, third,fourth, fifth, sixth, seventh and eighth subgroups of the second groupof embodiments, R¹ may also be phenyl, which is unsubstituted orsubstituted with 1, 2, 3 or 4 substituents or with 1 or 2 substituents,where the substituents are selected from the group consisting ofC₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and halo,and where the substituents are in particular selected from the groupconsisting of C₁-C₃alkyl, C₁-C₃alkoxy, fluoroC₁-C₂alkyl,fluoroC₁-C₂alkoxy, fluorine or chlorine.

Irrespective of its occurrence, R³ is as defined above.

According to a third group of embodiments R³ is selected from the groupconsisting of C₁-C₆alkyl and C₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl is unsubstituted, partly or completely fluorinated        and/or substituted with one or two substituents independently        selected from the group consisting of C₁-C₆alkoxy, hydroxy, and        oxo; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents independently selected from the group        consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluorine,        fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, hydroxy, and oxo.

In a subgroup of the third embodiment R³ is C₁-C₆alkyl orfluoroC₁-C₆alkyl.

According to a forth group of embodiments R³ is selected from the groupconsisting of phenyl, phenylC₁-C₆alkyl, bicyclicaryl,bicyclicarylC₁-C₆alkyl, monocyclic heteroarylC₁-C₆alkyl, monocyclicheteroaryl, and bicyclic heteroaryl; wherein the phenyl, the phenyl ofphenylC₁-C₆alkyl, the bicyclicaryl, the bicyclicaryl ofbicyclicarylC₁-C₆alkyl, the monocyclic heteroaryl of monocyclicheteroarylC₁-C₆alkyl, the monocyclic heteroaryl and the bicyclicheteroaryl are optionally substituted with 1, 2, 3 or 4 substituents

In a subgroup of the fourth embodiment R³ is selected from the groupconsisting of phenyl and monocyclic heteroaryl, such as pyridyl,pyrimidinyl or thienyl; wherein phenyl is substituted with 1, 2, 3 or 4substituents R^(Ar) and where the monocyclic heteroaryl is unsubstitutedor substituted with 1, 2, 3 or 4 substituents R^(Ar).

In a further subgroup of the fourth embodiment R³ is phenyl which issubstituted with 1, 2, 3 or 4 substituents R^(Ar) and where themonocyclic heteroaryl is unsubstituted or substituted with 1, 2, 3 or 4substituents R^(Ar).

Irrespective of its occurrence and also in the fourth embodiment and inthe subgroups of the forth embodiment the substituents R^(Ar) are asdefined above or, independently of its occurrence, selected from thegroup consisting of C₁-C₆alkyl, halogen, —OR^(1a),—S(O)₂N(R^(d))(R^(3a)), —C(O)R^(1a), —C(O)OR^(1a),—C(O)N(R^(d))(R^(3a)), —N(R^(d))(R^(3a)), —N(R^(c))C(O)R^(1a),—N(R^(c))S(O)₂R^(2a) and fluoroC₁-C₆-alkyl; wherein R^(1a), R^(2a),R^(3a), R^(c) and R^(d) are as defined above or

-   -   R^(c) and R^(d), at each occurrence, are each independently        hydrogen, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl;    -   R^(1a) and R^(3a), at each occurrence, are each independently        hydrogen, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl;    -   R^(d) and R^(3a), if present as a group N(R^(d))(R^(3a)), such        as in substituents —C(O)N(R^(d))(R^(3a)) or —N(R^(d))(R^(3a)),        may together with the atoms of said moiety form a        pyrrolidin-1-yl, piperidin-1-yl or azepan-1-yl radical; and    -   R^(2a), at each occurrence, is independently C₁-C₆alkyl, or        fluoroC₁-C₆-alkyl.    -   Examples of such radicals R^(Ar) include but are not limited to        fluoro, chloro, amino, hydroxyl, methyl, methoxy, carbamoyl,        carboxy, acetylamino, methylsulfonylamino,        N-methylaminocarbonyl, N,N-dimethylaminocarbonyl,        N-ethylaminocarbonyl, 1-pyrrolidin-2-onyl.    -   Examples of such radicals R³ include but are not limited to        methyl, ethyl, phenyl, 3-fluorophenyl, 4-fluorophenyl,        2-aminophenyl, 3-aminophenyl, 2-hydroxyphenyl, 2-methylphenyl,        2-methoxyphenyl, 4-methoxyphenyl, 3-carbamoylphenyl,        3-(acetylamino)phenyl, 3-(methylsulfonylamino)phenyl,        3-(aminosulfonyl)phenyl, 3,4-difluorophenyl, 3,5-difluorophenyl,        2,4-bis(methoxy)phenyl, 3,4-bis(methoxy)phenyl,        2,5-bis(methoxy)phenyl, 2-methoxy-5-fluorophenyl,        2-amino-5-fluorophenyl, 2-methoxy-5-carboxyphenyl,        2-methoxy-5-(trifluoromethyl)phenyl,        2-methoxy-5-(acetylamino)phenyl,        2-methoxy-3-(acetylamino)phenyl,        2-(trifluoromethoxy)-5-(acetylamino)phenyl,        2-methoxy-5-(methylsulfonyl-amino)phenyl,4-fluoro-3-(acetylamino)phenyl,        2-methyl-5-(acetylamino)phenyl, 2-methyl-5-hydroxyphenyl,        2-methoxy-5-(aminocarbonyl)phenyl,        3-amino-2-(aminocarbonyl)phenyl,        2-methoxy-5-(N-methylaminocarbonyl)phenyl,        2-methoxy-5-(N-ethylaminocarbonyl)phenyl,        2-methoxy-5-(N,N-dimethylamino-carbonyl)phenyl,        2-methoxy-5-(pyrrolidin-1-ylcarbonyl)phenyl,        2-methoxy-5-(pyrrolidin-2on-1-yl)phenyl,        3-methoxy-5-(N,N-dimethylaminocarbonyl)phenyl,        2-amino-5-chlorophenyl, 2-amino-5-(trifluoromethyl)phenyl,        2-amino-3,5-difluorophenyl,        2-methyl-3-(acetylamino)-4-fluorophenyl, 3-pyridyl,        5-pyrimidinyl, 2-fluoro-3-pyridyl, 2-amino-4-pyridyl,        5-fluoro-3-pyridyl, 2-chloro-3-pyridyl, indol-5-yl,        2,6-difluoropyridin-4-yl, 2-thienyl, 1-ethylpyrazol-5-yl, and        1H-pyrrolo[2,3-b]pyridine-6-yl.    -   Irrespective of its occurrence, X is in particular O.

In the first group of embodiments and in the subgroups of the firstgroup of embodiments, X is as defined above or X is O.

In the second group of embodiments and in the subgroups of the secondgroup of embodiments, X is as defined above or X is O.

In the third group of embodiments and in the subgroups of the thirdgroup of embodiments, X is as defined above or X is O.

In the fourth group of embodiments and in the subgroups of the forthgroup of embodiments, X is as defined above or X is O.

In the third group of embodiments, in the fourth group of embodimentsand also in the subgroups of the third and fourth groups of embodiments,R¹ is as defined above or selected from the group consisting ofC₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine.

In the third group of embodiments, in the fourth group of embodimentsand also in the subgroups of the third and fourth groups of embodiments,R¹ may also be selected from the group consisting of C₁-C₆alkyl,fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of C₁-C₃alkyl,fluorine, and fluoroC₁-C₃alkyl.

In the third group of embodiments, in the fourth group of embodimentsand also in the subgroups of the third and fourth groups of embodiments,R¹ may also be selected from the group consisting of C₁-C₄alkyl,C₁-C₂-alkoxy-C₁-C₂-alkyl and cyclopropyl, wherein cyclopropyl isunsubstituted or substituted with 1 or 2 substituents independentlyselected from the group consisting of methyl, ethyl, fluorine, andfluoroC₁-C₂alkyl.

In the third group of embodiments, in the fourth group of embodimentsand also in the subgroups of the third and fourth groups of embodiments,R¹ may also be phenyl, which is unsubstituted or substituted with 1, 2,3 or 4 substituents or with 1 or 2 substituents, where the substituentsare selected from the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and halo, and where thesubstituents are in particular selected from the group consisting ofC₁-C₃alkyl, C₁-C₃alkoxy, fluoroC₁-C₂alkyl, fluoroC₁-C₂alkoxy, fluorineor chlorine.

A fifth group of embodiments relates to compounds of the formula (I) orto their pharmaceutically acceptable salts or isotopically labeledforms, wherein R¹ is selected from the group consisting of C₁-C₆alkyl,C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine;

R² is as defined for the first group of embodiments or as defined forthe subgroups of the first group of embodiments;

R³ is as defined for the third group of embodiments or as defined forthe subgroup of the third group of embodiments, and

X is as defined above or X is O.

A sixth group of embodiments relates to compounds of the formula (I) andto their pharmaceutically acceptable salts or isotopically labeledforms, wherein R¹ is selected from the group consisting of C₁-C₆alkyl,C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine;

R² is as defined for the second group of embodiments or as defined forthe first, second, third, fourth, fifth, sixth or seventh subgroups ofthe second group of embodiments;

R³ is as defined for the third group of embodiments or as defined forthe subgroup of the third group of embodiments; and

X is as defined above or X is O.

A seventh group of embodiments relates to compounds of the formula (I)and to their pharmaceutically acceptable salts or isotopically labeledforms, wherein R¹ is selected from the group consisting of C₁-C₆alkyl,C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine;

R² is as defined for the first group of embodiments or as defined forthe subgroups of the first group of embodiments;

R³ is as defined for the third group of embodiments or as defined forthe subgroup of the fourth group of embodiments; and

X is as defined above or X is O.

An eighth group of embodiments relates to compounds of the formula (I)and to their pharmaceutically acceptable salts or isotopically labeledforms, wherein R¹ is selected from the group consisting of C₁-C₆alkyl,C₂-C₆alkenyl, C₂-C₆alkynyl and C₃-C₆cycloalkyl; wherein

-   -   C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,        partly or completely fluorinated and/or substituted with one or        two substituents independently selected from the group        consisting of C₁-C₆alkoxy, hydroxy, and oxo and where        C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are in particular        unsubstituted, partly or completely fluorinated and/or        substituted with one of C₁-C₆alkoxy; and    -   C₃-C₆cycloalkyl is unsubstituted or substituted with 1, 2, 3, 4        or 5 substituents, in particular with 1 or 2 substituents, which        are independently selected from the group consisting of        C₁-C₆alkyl, C₁-C₆alkoxy, fluorine, fluoroC₁-C₆alkyl,        fluoroC₁-C₆alkoxy, hydroxy, and oxo and especially from the        group consisting of C₁-C₃alkyl, C₁-C₃alkoxy and fluorine;

R² is as defined for the second group of embodiments or as defined forthe first, second, third, fourth, fifth, sixth or seventh subgroups ofthe second group of embodiments;

R³ is as defined for the fourth group of embodiments or as defined forthe subgroup of the fourth group of embodiments; and

X is as defined above or X is O.

A 9^(th) group of embodiments relates to compounds of the formula (I)and to their pharmaceutically acceptable salts or isotopically labeledforms, wherein

R¹ is selected from the group consisting of C₁-C₆alkyl,fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of C₁-C₃alkyl,fluorine, and fluoroC₁-C₃alkyl, and where R¹ is in particular selectedfrom the group consisting of C₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl andcyclopropyl, wherein cyclopropyl is unsubstituted or substituted with 1or 2 substituents independently selected from the group consisting ofmethyl, ethyl, fluorine, and fluoroC₁-C₂alkyl;

R² is as defined for the first group of embodiments or as defined forthe subgroups of the first group of embodiments, and

R³ is as defined for the third group of embodiments or as defined forthe subgroup of the third group of embodiments.

In the 9^(th) group of embodiments, X is as defined above or X is O.

A 10^(th) group of embodiments relates to compounds of the formula (I)and to their pharmaceutically acceptable salts or isotopically labeledforms, wherein

R¹ is selected from the group consisting of C₁-C₆alkyl,fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of C₁-C₃alkyl,fluorine, and fluoroC₁-C₃alkyl, and where R¹ is in particular selectedfrom the group consisting of C₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl andcyclopropyl, wherein cyclopropyl is unsubstituted or substituted with 1or 2 substituents independently selected from the group consisting ofmethyl, ethyl, fluorine, and fluoroC₁-C₂alkyl;

R² is as defined for the second group of embodiments or as defined forthe first, second, third, fourth, fifth, sixth or seventh subgroups ofthe second group of embodiments, and

R³ is as defined for the third group of embodiments or as defined forthe subgroup of the third group of embodiments.

In the 10^(th) group of embodiments, X is as defined above or X is O.

An 11^(th) group of embodiments relates to compounds of the formula (I)and to their pharmaceutically acceptable salts or isotopically labeledforms, wherein

R¹ is selected from the group consisting of C₁-C₆alkyl,fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of C₁-C₃alkyl,fluorine, and fluoroC₁-C₃alkyl, and where R¹ is in particular selectedfrom the group consisting of C₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl andcyclopropyl, wherein cyclopropyl is unsubstituted or substituted with 1or 2 substituents independently selected from the group consisting ofmethyl, ethyl, fluorine, and fluoroC₁-C₂alkyl;

R² is as defined for the first group of embodiments or as defined forthe subgroups of the first group of embodiments, and

R³ is as defined for the third group of embodiments or as defined forthe subgroup of the fourth group of embodiments.

In the 11^(th) group of embodiments, X is as defined above or X is O.

A 12^(th) group of embodiments relates to compounds of the formula (I)and to their pharmaceutically acceptable salts or isotopically labeledforms, wherein

R¹ is selected from the group consisting of C₁-C₆alkyl,fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl, whereincyclopropyl is unsubstituted or substituted with 1 or 2 substituentsindependently selected from the group consisting of C₁-C₃alkyl,fluorine, and fluoroC₁-C₃alkyl, and where R¹ is in particular selectedfrom the group consisting of C₁-C₄alkyl, C₁-C₂-alkoxy-C₁-C₂-alkyl andcyclopropyl, wherein cyclopropyl is unsubstituted or substituted with 1or 2 substituents independently selected from the group consisting ofmethyl, ethyl, fluorine, and fluoroC₁-C₂alkyl;

R² is as defined for the second group of embodiments or as defined forthe first, second, third, fourth, fifth, sixth or seventh subgroups ofthe second group of embodiments, and

R³ is as defined for the fourth group of embodiments or as defined forthe subgroup of the fourth group of embodiments.

In the 11^(th) group of embodiments, X is as defined above or X is O.

A special group of embodiments relates to compounds, wherein

R¹ is selected from the group consisting of methyl, ethyl, isopropyl,n-propyl, cyclopropyl, methoxymethyl and phenyl which is unsubstitutedor substituted by halo.

R² is selected from the group consisting of 4-chlorphenylmethyl,3-(trifluoromethyl)phenylmethyl, 4-(trifluoromethyl)phenylmethyl,4-methoxy-3-(trifluoromethyl)phenylmethyl,2-fluoro-5-(trifluoromethyl)phenylmethyl, 5-chloro-2-fluorophenylmethyl,4-chloro-2-fluorophenylmethyl, 4-chlorophenylphenylmethyl,2,4-difluorophenylmethyl, 4-fluoro-3-(trifluoromethyl)phenylmethyl,4-chloro-3-(trifluoromethyl)phenylmethyl, 2-fluorophenylmethyl,4-fluorophenylmethyl, (1RS)-1-(4-chlorphenyl)ethyl,(1R)-1-(4-chlorphenyl)ethyl, (1S)-1-(4-chlorphenyl)ethyl,2-(4-chlorphenyl)ethyl, (1RS)-1-(4-(trifluoromethyl)phenyl)ethyl,(1R)-1-(4-(trifluoromethyl)phenyl)ethyl,(1S)-1-(4-(trifluoromethyl)phenyl)ethyl, and 4-pyridylmethyl;

R³ is selected from the group consisting of methyl, ethyl, phenyl,3-fluorophenyl, 4-fluorophenyl, 2-aminophenyl, 3-aminophenyl,2-hydroxyphenyl, 2-methylphenyl, 2-methoxyphenyl, 4-methoxyphenyl,3-carbamoylphenyl, 3-(acetylamino)phenyl, 3-(methylsulfonylamino)phenyl,3-(aminosulfonyl)phenyl, 3,4-difluorophenyl, 3,5-difluorophenyl,2,4-bis(methoxy)phenyl, 3,4-bis(methoxy)phenyl, 2,5-bis(methoxy)phenyl,2-methoxy-5-fluorophenyl, 2-amino-5-fluorophenyl,2-methoxy-5-carboxyphenyl, 2-methoxy-5-(trifluoromethyl)phenyl,2-methoxy-5-(acetylamino)phenyl, 2-methoxy-3-(acetylamino)phenyl,2-(trifluoromethoxy)-5-(acetylamino)phenyl,2-methoxy-5-(methylsulfonylamino)phenyl,4-fluoro-3-(acetylamino)phenyl,2-methyl-5-(acetylamino)phenyl, 2-methyl-5-hydroxyphenyl,2-methoxy-5-(aminocarbonyl)phenyl, 3-amino-2-(aminocarbonyl)phenyl,2-methoxy-5-(N-methylaminocarbonyl)phenyl,2-methoxy-5-(N-ethylaminocarbonyl)phenyl,2-methoxy-5-(N,N-dimethylaminocarbonyl)phenyl,2-methoxy-5-(pyrrolidin-1-ylcarbonyl)phenyl,2-methoxy-5-(pyrrolidin-2-on-1-yl)phenyl,3-methoxy-5-(N,N-dimethylaminocarbonyl)phenyl, 2-amino-5-chlorophenyl,2-amino-5-(trifluoromethyl)phenyl, 2-amino-3,5-difluorophenyl,2-methyl-3-(acetylamino)-4-fluorophenyl, 3-pyridyl, 5-pyrimidinyl,2-fluoro-3-pyridyl, 2-amino-4-pyridyl, 5-fluoro-3-pyridyl,2-chloro-3-pyridyl, indol-5-yl, 2,6-difluoropyridin-4-yl, 2-thienyl,1-ethylpyrazol-5-yl, and 1H-pyrrolo[2,3-b]pyridine-6-yl; and X is O.

Specific embodiments contemplated as part of the invention also include,but are not limited to, compounds or pharmaceutically acceptable saltsor isotopically labeled forms thereof, as defined, for example:

N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;

5-(4-chlorobenzyl)-7-(4-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;

5-[1-(4-chlorophenyl)ethyl]-7-(2,6-difluoropyridin-4-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,4-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2-amino-5-chlorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-(2-chloropyridin-3-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{5-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-2-fluorophenyl}acetamide;

7-(2,5-dimethoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[2-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-[2-amino-5-(trifluoromethyl)phenyl]-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-(1H-indol-6-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2-aminophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

5-[1-(4-chlorophenyl)ethyl]-7-(5-hydroxy-2-methylphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(2-fluoro-5-{5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methylphenyl)acetamide;

7-(4-fluorophenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-(5-fluoropyridin-3-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(3-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)methanesulfonamide;

5-[2-fluoro-5-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2-methoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-3-(methoxymethyl)-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

5-[4-chloro-3-(trifluoromethyl)benzyl]-7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(2-fluoro-5-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

5-(4-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[(1S)-1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,4-dimethoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-2-methoxyphenyl)acetamide;

N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

N-[4-methyl-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;

5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,4-dimethoxyphenyl)-5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N,N-dimethylbenzamide;

N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;

N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;

N-(3-{5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

5-(4-chlorobenzyl)-7-(3,4-difluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[4-fluoro-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3,7-dimethyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-4-methoxyphenyl}acetamide;

5-[2-fluoro-5-(trifluoromethyl)benzyl]-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,4-dimethoxyphenyl)-5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-[3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-(trifluoromethoxy)phenyl]acetamide;

5-[4-methoxy-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzenesulfonamide;

5-[4-fluoro-3-(trifluoromethyl)benzyl]-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)methanesulfonamide;

5-(4-chlorobenzyl)-3-methyl-7-(thiophen-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

5-[(1R)-1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzamide;

5-[2-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(2-fluoro-5-{5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

N-(2-fluoro-5-{5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

5-[1-(4-chlorophenyl)ethyl]-7-(5-fluoro-2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(4-methoxy-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

2-amino-6-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamide;

7-(4-fluorophenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[(1S)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[4-chloro-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzoicacid;

7-(4-fluorophenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[(R)-(4-chlorophenyl)(phenyl)methyl]-3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-3-methyl-7-(2-methylphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2-amino-3,5-difluorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

5-[1-(4-chlorophenyl)ethyl]-7-[2-methoxy-5-(trifluoromethyl)phenyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,5-dimethoxyphenyl)-5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide;

5-(4-chlorobenzyl)-7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(3-chloro-4-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

7-(2-aminopyridin-3-yl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(2,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(5-chloro-2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[(S)-(4-chlorophenyl)(phenyl)methyl]-3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(3,5-difluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-4-oxo-3-propyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

5-(4-chloro-2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,5-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{2-fluoro-5-[3-methyl-4-oxo-5-(pyridin-4-ylmethyl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

7-(2,5-dimethoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-4-oxo-3-(propan-2-yl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

7-(2-amino-5-fluorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-[2-methoxy-5-(pyrrolidin-1-ylcarbonyl)phenyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(3,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-(2-hydroxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2-methoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1S)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;

N-{3-[5-(4-chlorobenzyl)-4-oxo-3-phenyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamide;

N-(4-methyl-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;

3,7-dimethyl-5-(3-methylbutyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(pyridin-3-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[3-methyl-4-oxo-5-(pyridin-4-ylmethyl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide;

N-[6-fluoro-2-methyl-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;

5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(pyrimidin-5-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-7-(1-ethyl-1H-pyrazol-5-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(1H-pyrrolo[3,2-b]pyridin-6-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;

7-(2-methoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide;

5-(4-chlorobenzyl)-3-methyl-7-(pyridin-3-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3,7-dimethyl-5-[3-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(4-chlorobenzyl)-3-methyl-7-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-(2,4-difluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

3,7-dimethyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,5-dimethoxyphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(3-aminophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

7-(2,4-dimethoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

5-[(1R)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;

N-{3-[5-(4-chlorobenzyl)-3-ethyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;

7-(2,5-dimethoxyphenyl)-5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;and

3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-N-ethyl-4-methoxybenzamide.

Compound names are assigned by using Name 2014 naming algorithm byAdvanced Chemical Development or Struct=Name naming algorithm as part ofCHEMDRAW® ULTRA v. 12.0.2.1076.

Compounds of the invention may exist as stereoisomers wherein asymmetricor chiral centers are present. These stereoisomers are “R” or “S”depending on the configuration of substituents around the chiral carbonatom. The terms “R” and “S” used herein are configurations as defined inIUPAC 1974 Recommendations for Section E, Fundamental Stereochemistry,in Pure Appl. Chem., 1976, 45: 13-30. The invention contemplates variousstereoisomers and mixtures thereof and these are specifically includedwithin the scope of this invention. Stereoisomers include enantiomersand diastereomers, and mixtures of enantiomers or diastereomers.Individual stereoisomers of compounds of the invention may be preparedsynthetically from commercially available starting materials whichcontain asymmetric or chiral centers or by preparation of racemicmixtures followed by methods of resolution well-known to those ofordinary skill in the art. These methods of resolution are exemplifiedby (1) attachment of a mixture of enantiomers to a chiral auxiliary,separation of the resulting mixture of diastereomers byrecrystallization or chromatography and optional liberation of theoptically pure product from the auxiliary as described in Furniss,Hannaford, Smith, and Tatchell, “Vogel's Textbook of Practical OrganicChemistry”, 5th edition (1989), Longman Scientific & Technical, EssexCM20 2JE, England, or (2) direct separation of the mixture of opticalenantiomers on chiral chromatographic columns or (3) fractionalrecrystallization methods.

Compounds of the invention may exist as cis or trans isomers, whereinsubstituents on a ring may attached in such a manner that they are onthe same side of the ring (cis) relative to each other, or on oppositesides of the ring relative to each other (trans). For example,cyclobutane may be present in the cis or trans configuration, and may bepresent as a single isomer or a mixture of the cis and trans isomers.Individual cis or trans isomers of compounds of the invention may beprepared synthetically from commercially available starting materialsusing selective organic transformations, or prepared in single isomericform by purification of mixtures of the cis and trans isomers. Suchmethods are well-known to those of ordinary skill in the art, and mayinclude separation of isomers by recrystallization or chromatography.

It should be understood that the compounds of the invention may possesstautomeric forms, as well as geometric isomers, and that these alsoconstitute an aspect of the invention.

The present disclosure includes all pharmaceutically acceptableisotopically-labelled compounds of formula (I) wherein one or more atomsare replaced by atoms having the same atomic number, but an atomic massor mass number different from the atomic mass or mass number whichpredominates in nature. Examples of isotopes suitable for inclusion inthe compounds of the disclosure include isotopes of hydrogen, such as ²Hand ³H, carbon, such as ¹¹C, ¹³C and ¹⁴C, chlorine, such as ³⁶Cl,fluorine, such as ¹⁸F, iodine, such as ¹²³I and ¹²⁵I, nitrogen, such as¹³N and ¹⁵N, oxygen, such as ¹⁵O, ¹⁷O and ¹⁸O, phosphorus, such as ³²P,and sulfur, such as ³⁵S. Certain isotopically-labelled compounds offormula (I), for example, those incorporating a radioactive isotope, areuseful in drug and/or substrate tissue distribution studies. Theradioactive isotopes tritium, i.e. ³H, and carbon-14, i.e. ¹⁴C, areparticularly useful for this purpose in view of their ease ofincorporation and ready means of detection. Substitution with heavierisotopes such as deuterium, i.e. ²H, may afford certain therapeuticadvantages resulting from greater metabolic stability, for example,increased in vivo half-life or reduced dosage requirements, and hencemay be preferred in some circumstances. Substitution with positronemitting isotopes, such as ¹¹C, ¹⁸F, ¹⁵O and ¹³N, can be useful inPositron Emission Topography (PET) studies for examining substratereceptor occupancy. Isotopically-labeled compounds of formula (I) cangenerally be prepared by conventional techniques known to those skilledin the art or by processes analogous to those described in theaccompanying Examples using an appropriate isotopically-labeled reagentsin place of the non-labeled reagent previously employed.

Thus, the formula drawings within this specification can represent onlyone of the possible tautomeric, geometric, or stereoisomeric forms. Itis to be understood that the invention encompasses any tautomeric,geometric, or stereoisomeric form, and mixtures thereof, and is not tobe limited merely to any one tautomeric, geometric, or stereoisomericform utilized within the formula drawings.

Present compounds may be used in the form of pharmaceutically acceptablesalts. The phrase “pharmaceutically acceptable salt” means those saltswhich are, within the scope of sound medical judgment, suitable for usein contact with the tissues of humans and lower animals without unduetoxicity, irritation, allergic response and the like and arecommensurate with a reasonable benefit/risk ratio.

Pharmaceutically acceptable salts have been described in S. M. Berge etal. J. Pharmaceutical Sciences, 1977, 66: 1-19.

Compounds of the invention may contain either a basic or an acidicfunctionality, or both, and can be converted to a pharmaceuticallyacceptable salt, when desired, by using a suitable acid or base. Thesalts may be prepared in situ during the final isolation andpurification of the compounds of the invention.

Examples of acid addition salts include, but are not limited to acetate,adipate, alginate, citrate, aspartate, benzoate, benzenesulfonate,bisulfate, butyrate, camphorate, camphorsulfonate, digluconate,glycerophosphate, hemisulfate, heptanoate, hexanoate, fumarate,hydrochloride, hydrobromide, hydroiodide, 2-hydroxyethansulfonate(isothionate), lactate, malate, maleate, methanesulfonate, nicotinate,2-naphthalenesulfonate, oxalate, palmitoate, pectinate, persulfate,3-phenylpropionate, picrate, pivalate, propionate, succinate, tartrate,thiocyanate, phosphate, glutamate, bicarbonate, p-toluenesulfonate andundecanoate. Also, the basic nitrogen-containing groups can bequaternized with such agents as lower alkyl halides such as, but notlimited to, methyl, ethyl, propyl, and butyl chlorides, bromides andiodides; dialkyl sulfates like dimethyl, diethyl, dibutyl and diamylsulfates; long chain halides such as, but not limited to, decyl, lauryl,myristyl and stearyl chlorides, bromides and iodides; arylalkyl halideslike benzyl and phenethyl bromides and others. Water or oil-soluble ordispersible products are thereby obtained. Examples of acids which maybe employed to form pharmaceutically acceptable acid addition saltsinclude such inorganic acids as hydrochloric acid, hydrobromic acid,sulfuric acid, and phosphoric acid and such organic acids as aceticacid, fumaric acid, maleic acid, 4-methylbenzenesulfonic acid, succinicacid and citric acid.

Basic addition salts may be prepared in situ during the final isolationand purification of compounds of this invention by reacting a carboxylicacid-containing moiety with a suitable base such as, but not limited to,the hydroxide, carbonate or bicarbonate of a pharmaceutically acceptablemetal cation or with ammonia or an organic primary, secondary ortertiary amine. Pharmaceutically acceptable salts include, but are notlimited to, cations based on alkali metals or alkaline earth metals suchas, but not limited to, lithium, sodium, potassium, calcium, magnesiumand aluminum salts and the like and nontoxic quaternary ammonia andamine cations including ammonium, tetramethylammonium,tetraethylammonium, methylamine, dimethylamine, trimethylamine,triethylamine, diethylamine, ethylamine and the like. Other examples oforganic amines useful for the formation of base addition salts includeethylenediamine, ethanolamine, diethanolamine, piperidine, piperazineand the like.

The term “pharmaceutically acceptable prodrug” or “prodrug” as usedherein, represents those prodrugs of the compounds of the inventionwhich are, within the scope of sound medical judgment, suitable for usein contact with the tissues of humans and lower animals without unduetoxicity, irritation, allergic response, and the like, commensurate witha reasonable benefit/risk ratio, and effective for their intended use.

The invention contemplates compounds formed by synthetic means or formedby in vivo biotransformation of a prodrug.

Compounds described herein can exist in unsolvated as well as solvatedforms, including hydrated forms, such as hemi-hydrates. In general, thesolvated forms, with pharmaceutically acceptable solvents such as waterand ethanol among others are equivalent to the unsolvated forms for thepurposes of the invention.

General Synthesis

The compounds of the invention can be better understood in connectionwith the following synthetic schemes and methods which illustrate ameans by which the compounds can be prepared.

The compounds of this invention can be prepared by a variety ofsynthetic procedures. Representative procedures are shown in, but arenot limited to, Schemes 1-3. In Schemes 1-3, the variables R¹, R² and R³are as described in the Summary.

As shown in Scheme 1, compounds of formula (1-6) can be prepared fromcompounds of formula (1-1). Accordingly, compounds of formula (1-1) canbe treated with a base such as magnesiumethanolate at or near ambienttemperature to reflux for 30 minutes to 4 hours in a solvent such astoluene. Then, a solvent such as acetonitrile can be added followed bythe addition of 2-chloroacetyl chloride at about −10° C. The reactionmixture can then be allowed to warm to ambient temperature withcontinued stirring for 1-24 hours to give compounds of formula (1-2).Compounds of formula (1-2) can then be treated with hydroxylamine orhydroxylamine hydrochloride in the presence of a base such as sodiumacetate in refluxing ethanol over 1-8 hours to give compounds of formula(1-3). The alcohols of formula (1-3) can be oxidized to thecorresponding aldehydes of formula (1-4) by treatment with anappropriate oxidant such as manganese(IV) oxide in refluxing tolueneover 3-10 hours or Dess-Martin periodinane in dichloromethane at ambienttemperature over 4-16 hours. The aldehydes of formula (1-4) can bereacted with hydrazine or hydrazine hydrate in ethanol at 0-30° C. over1-8 hours to give compounds of formula (1-5). Compounds of formula (1-5)can be reacted with bromine in the presence of a base such as lithiumhydroxide in refluxing methanol over 6-24 hours to give compounds offormula (1-6).

As shown in Scheme 2, compounds of formula (1-6) can be converted tocompounds of formula (I). Compounds of formula (1-6) can be alkylatedwith R²-LG¹; wherein LG¹ is a leaving group such as chlorine, bromine,iodine or a sulfonate; in the presence of a base such as potassiumcarbonate in a solvent such as N,N-dimethylformamide at 20-60° C. over1-18 hours to give compounds of formula (2-1). Compounds of formula(2-1) can be reacted with boronic acids, R³—B(OH)₂, or the correspondingboronates under Suzuki or other cross-coupling reaction conditions togive compounds of formula (I).

As shown in Scheme 3, compounds of formula (1-6) can be converted tocompounds of formula (I) with reactions of Scheme 2 reversed insequence. Compounds of formula (1-6) can be reacted with boronic acids,R³—B(OH)₂, or the corresponding boronates under Suzuki or othercross-coupling reaction conditions to give compounds of formula (3-1).Compounds of formula (3-1) can be alkylated with R²-LG¹; wherein LG¹ isa leaving group such as chlorine, bromine, iodine or a sulfonate; in thepresence of a base such as potassium carbonate or sodium hydride in asolvent such as N,N-dimethylformamide at 20-60° C. over 1-18 hours togive compounds of formula (I).

The compounds and intermediates of the invention may be isolated andpurified by methods well-known to those skilled in the art of organicsynthesis. Examples of conventional methods for isolating and purifyingcompounds can include, but are not limited to, chromatography on solidsupports such as silica gel, alumina, or silica derivatized withalkylsilane groups, by recrystallization at high or low temperature withan optional pretreatment with activated carbon, thin-layerchromatography, distillation at various pressures, sublimation undervacuum, and trituration, as described for instance in “Vogel's Textbookof Practical Organic Chemistry”, 5th edition (1989), by Furniss,Hannaford, Smith, and Tatchell, pub. Longman Scientific & Technical,Essex CM20 2JE, England.

Many of the compounds of the invention have at least one basic nitrogenwhereby the compound can be treated with an acid to form a desired salt.For example, a compound may be reacted with an acid at or above roomtemperature to provide the desired salt, which is deposited, andcollected by filtration after cooling. Examples of acids suitable forthe reaction include, but are not limited to tartaric acid, lactic acid,succinic acid, as well as mandelic, atrolactic, methanesulfonic,ethanesulfonic, toluenesulfonic, naphthalenesulfonic, benzenesulfonic,carbonic, fumaric, maleic, gluconic, acetic, propionic, salicylic,hydrochloric, hydrobromic, phosphoric, sulfuric, citric, hydroxybutyric,camphorsulfonic, malic, phenylacetic, aspartic, or glutamic acid, andthe like.

Optimum reaction conditions and reaction times for each individual stepcan vary depending on the particular reactants employed and substituentspresent in the reactants used. Unless otherwise specified, solvents,temperatures and other reaction conditions can be readily selected byone of ordinary skill in the art. Specific procedures are provided inthe Examples section. Reactions can be worked up in the conventionalmanner, e.g. by eliminating the solvent from the residue and furtherpurified according to methodologies generally known in the art such as,but not limited to, crystallization, distillation, extraction,trituration and chromatography. Unless otherwise described, the startingmaterials and reagents are either commercially available or can beprepared by one skilled in the art from commercially available materialsusing methods described in the chemical literature.

Routine experimentations, including appropriate manipulation of thereaction conditions, reagents and sequence of the synthetic route,protection of any chemical functionality that cannot be compatible withthe reaction conditions, and deprotection at a suitable point in thereaction sequence of the method are included in the scope of theinvention. Suitable protecting groups and the methods for protecting anddeprotecting different substituents using such suitable protectinggroups are well known to those skilled in the art; examples of which canbe found in PGM Wuts and TW Greene, in Greene's book titled ProtectiveGroups in Organic Synthesis (4^(th) ed.), John Wiley & Sons, NY (2006),which is incorporated herein by reference in its entirety. Synthesis ofthe compounds of the invention can be accomplished by methods analogousto those described in the synthetic schemes described hereinabove and inspecific examples.

Starting materials, if not commercially available, can be prepared byprocedures selected from standard organic chemical techniques,techniques that are analogous to the synthesis of known, structurallysimilar compounds, or techniques that are analogous to the abovedescribed schemes or the procedures described in the synthetic examplessection.

When an optically active form of a compound of the invention isrequired, it can be obtained by carrying out one of the proceduresdescribed herein using an optically active starting material (prepared,for example, by asymmetric induction of a suitable reaction step), or byresolution of a mixture of the stereoisomers of the compound orintermediates using a standard procedure (such as chromatographicseparation, recrystallization or enzymatic resolution).

Similarly, when a pure geometric isomer of a compound of the inventionis required, it can be obtained by carrying out one of the aboveprocedures using a pure geometric isomer as a starting material, or byresolution of a mixture of the geometric isomers of the compound orintermediates using a standard procedure such as chromatographicseparation.

It can be appreciated that the synthetic schemes and specific examplesas illustrated in the Examples section are illustrative and are not tobe read as limiting the scope of the invention as it is defined in theappended claims. All alternatives, modifications, and equivalents of thesynthetic methods and specific examples are included within the scope ofthe claims.

Pharmaceutical Compositions

This invention also provides for pharmaceutical compositions comprisinga therapeutically effective amount of a compound of formula (I), or apharmaceutically acceptable salt or isotopically labelled form thereoftogether with a pharmaceutically acceptable carrier, diluent, orexcipient thereof. The phrase “pharmaceutical composition” refers to acomposition suitable for administration in medical or veterinary use.

The pharmaceutical compositions that comprise a compound of formula (I),alone or in combination with a second therapeutic agent, may beadministered to the subjects orally, rectally, parenterally,intracisternally, intravaginally, intraperitoneally, topically (as bypowders, ointments or drops), bucally or as an oral or nasal spray. Theterm “parenterally” as used herein, refers to modes of administrationwhich include intravenous, intramuscular, intraperitoneal, intrasternal,subcutaneous and intraarticular injection and infusion.

The term “pharmaceutically acceptable carrier” as used herein, means anon-toxic, inert solid, semi-solid or liquid filler, diluent,encapsulating material or formulation auxiliary of any type. Someexamples of materials which may serve as pharmaceutically acceptablecarriers are sugars such as, but not limited to, lactose, glucose andsucrose; starches such as, but not limited to, corn starch and potatostarch; cellulose and its derivatives such as, but not limited to,sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate;powdered tragacanth; malt; gelatin; talc; excipients such as, but notlimited to, cocoa butter and suppository waxes; oils such as, but notlimited to, peanut oil, cottonseed oil, safflower oil, sesame oil, oliveoil, corn oil and soybean oil; glycols; such a propylene glycol; esterssuch as, but not limited to, ethyl oleate and ethyl laurate; agar;buffering agents such as, but not limited to, magnesium hydroxide andaluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline;Ringer's solution; ethyl alcohol, and phosphate buffer solutions, aswell as other non-toxic compatible lubricants such as, but not limitedto, sodium lauryl sulfate and magnesium stearate, as well as coloringagents, releasing agents, coating agents, sweetening, flavoring andperfuming agents, preservatives and antioxidants may also be present inthe composition, according to the judgment of the formulator.

Pharmaceutical compositions for parenteral injection comprisepharmaceutically acceptable sterile aqueous or nonaqueous solutions,dispersions, suspensions or emulsions as well as sterile powders forreconstitution into sterile injectable solutions or dispersions justprior to use. Examples of suitable aqueous and nonaqueous carriers,diluents, solvents or vehicles include water, ethanol, polyols (such asglycerol, propylene glycol, polyethylene glycol and the like), vegetableoils (such as olive oil), injectable organic esters (such as ethyloleate), and suitable mixtures thereof. Proper fluidity may bemaintained, for example, by the use of coating materials such aslecithin, by the maintenance of the required particle size in the caseof dispersions and by the use of surfactants.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms may be ensured by the inclusion of variousantibacterial and antifungal agents, for example, paraben,chlorobutanol, phenol sorbic acid, and the like. It may also bedesirable to include isotonic agents such as sugars, sodium chloride,and the like. Prolonged absorption of the injectable pharmaceutical formmay be brought about by the inclusion of agents which delay absorption,such as aluminum monostearate and gelatin.

In some cases, in order to prolong the effect of the drug, it isdesirable to slow the absorption of the drug from subcutaneous orintramuscular injection. This may be accomplished by the use of a liquidsuspension of crystalline or amorphous material with poor watersolubility. The rate of absorption of the drug then depends upon itsrate of dissolution which, in turn, may depend upon crystal size andcrystalline form. Alternatively, delayed absorption of aparenterally-administered drug form may be accomplished by dissolving orsuspending the drug in an oil vehicle.

Injectable depot forms are made by forming microencapsule matrices ofthe drug in biodegradable polymers such as polylactide-polyglycolide.Depending upon the ratio of drug to polymer and the nature of theparticular polymer employed, the rate of drug release may be controlled.Examples of other biodegradable polymers include poly(orthoesters) andpoly(anhydrides). Depot injectable formulations are also prepared byentrapping the drug in liposomes or microemulsions which are compatiblewith body tissues.

The injectable formulations may be sterilized, for example, byfiltration through a bacterial-retaining filter or by incorporatingsterilizing agents in the form of sterile solid compositions which canbe dissolved or dispersed in sterile water or other sterile injectablemedium just prior to use.

Solid dosage forms for oral administration include capsules, tablets,pills, powders and granules. In certain embodiments, solid dosage formsmay contain from 1% to 95% (w/w) of a compound of formula (I). Incertain embodiments, the compound of formula (I) may be present in thesolid dosage form in a range of from 5% to 70% (w/w). In such soliddosage forms, the active compound may be mixed with at least one inert,pharmaceutically acceptable excipient or carrier, such as sodium citrateor dicalcium phosphate and/or a) fillers or extenders such as starches,lactose, sucrose, glucose, mannitol and silicic acid; b) binders such ascarboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidone,sucrose and acacia; c) humectants such as glycerol; d) disintegratingagents such as agar-agar, calcium carbonate, potato or tapioca starch,alginic acid, certain silicates and sodium carbonate; e) solutionretarding agents such as paraffin; f) absorption accelerators such asquaternary ammonium compounds; g) wetting agents such as cetyl alcoholand glycerol monostearate; h) absorbents such as kaolin and bentoniteclay and i) lubricants such as talc, calcium stearate, magnesiumstearate, solid polyethylene glycols, sodium lauryl sulfate and mixturesthereof. In the case of capsules, tablets and pills, the dosage form mayalso comprise buffering agents.

The pharmaceutical composition may be a unit dosage form. In such formthe preparation is subdivided into unit doses containing appropriatequantities of the active component. The unit dosage form can be apackaged preparation, the package containing discrete quantities ofpreparation, such as packaged tablets, capsules, and powders in vials orampules. Also, the unit dosage form may be a capsule, tablet, cachet, orlozenge itself, or it may be the appropriate number of any of these inpackaged form. The quantity of active component in a unit dose may bevaried or adjusted from 0.1 mg to 1000 mg, from 1 mg to 100 mg, from 10mg to 50 mg, from 20 mg to 40 mg or from 1% to 95% (w/w) of a unit dose,according to the particular application and the potency of the activecomponent. The composition may, if desired, also contain othercompatible therapeutic agents.

The dose to be administered to a subject may be determined by theefficacy of the particular compound employed and the condition of thesubject, as well as the body weight or surface area of the subject to betreated. The size of the dose also will be determined by the existence,nature, and extent of any adverse side-effects that accompany theadministration of a particular compound in a particular subject. Indetermining the effective amount of the compound to be administered inthe treatment or prophylaxis of the disorder being treated, thephysician may evaluate factors such as the circulating plasma levels ofthe compound, compound toxicities, and/or the progression of thedisease, etc.

For administration, compounds may be administered at a rate determinedby factors that may include, but are not limited to, the LD₅₀ of thecompound, the pharmacokinetic profile of the compound, contraindicateddrugs, and the side-effects of the compound at various concentrations,as applied to the mass and overall health of the subject. Administrationmay be accomplished via single or divided doses.

The compounds utilized in the pharmaceutical method of the invention maybe administered at the initial dosage of about 0.001 mg/kg to about 100mg/kg daily. In certain embodiments, the daily dosage is from about0.005 mg/kg to about 50 mg/kg. In further embodiments, the daily dosageis from about 0.01 mg/kg to about 25 mg/kg. In yet further embodiments,the daily dosage is from about 0.05 mg/kg to about 20 mg/kg. In yetfurther embodiments, the daily dosage is from about 0.1 mg/kg to about10 mg/kg. The dosages, however, may be varied depending upon therequirements of the subject, the severity of the condition beingtreated, and the compound being employed. Determination of the properdosage for a particular situation is within the skill of thepractitioner. Treatment may be initiated with smaller dosages, which areless than the optimum dose of the compound. Thereafter, the dosage isincreased by small increments until the optimum effect undercircumstances is reached. For convenience, the total daily dosage may bedivided and administered in portions during the day, if desired.

Solid compositions of a similar type may also be employed as fillers insoft and hard-filled gelatin capsules using such carriers as lactose ormilk sugar as well as high molecular weight polyethylene glycols and thelike.

The solid dosage forms of tablets, dragees, capsules, pills and granulescan be prepared with coatings and shells such as enteric coatings andother coatings well-known in the pharmaceutical formulating art. Theymay optionally contain opacifying agents and may also be of acomposition such that they release the active ingredient(s) only, orpreferentially, in a certain part of the intestinal tract, optionally,in a delayed manner. Examples of embedding compositions which can beused include polymeric substances and waxes.

The active compounds may also be in micro-encapsulated form, ifappropriate, with one or more of the above-mentioned carriers.

Liquid dosage forms for oral administration include pharmaceuticallyacceptable emulsions, solutions, suspensions, syrups and elixirs. Inaddition to the active compounds, the liquid dosage forms may containinert diluents commonly used in the art such as, for example, water orother solvents, solubilizing agents and emulsifiers such as ethylalcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzylalcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol,dimethyl formamide, oils (in particular, cottonseed, groundnut, corn,germ, olive, castor and sesame oils), glycerol, tetrahydrofurfurylalcohol, polyethylene glycols, and fatty acid esters of sorbitan andmixtures thereof.

Besides inert diluents, the oral compositions may also include adjuvantssuch as wetting agents, emulsifying and suspending agents, sweetening,flavoring and perfuming agents.

Suspensions, in addition to the active compounds, may contain suspendingagents as, for example, ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminummetahydroxide, bentonite, agar-agar, tragacanth and mixtures thereof.

Compositions for rectal or vaginal administration are preferablysuppositories which may be prepared by mixing the compounds withsuitable non-irritating carriers or carriers such as cocoa butter,polyethylene glycol, or a suppository wax which are solid at roomtemperature but liquid at body temperature and therefore melt in therectum or vaginal cavity and release the active compound.

Compounds may also be administered in the form of liposomes. Liposomesgenerally may be derived from phospholipids or other lipid substances.Liposomes are formed by mono- or multi-lamellar hydrated liquid crystalswhich are dispersed in an aqueous medium. Any non-toxic, physiologicallyacceptable and metabolizable lipid capable of forming liposomes may beused. The present compositions in liposome form may contain, in additionto a compound of the invention, stabilizers, preservatives, excipients,and the like. Examples of lipids include, but are not limited to,natural and synthetic phospholipids, and phosphatidyl cholines(lecithins), used separately or together.

Methods to form liposomes have been described, see example, Prescott,Ed., Methods in Cell Biology, Volume XIV, Academic Press, New York, N.Y.(1976), p. 33 et seq.

Dosage forms for topical administration of a compound described hereininclude powders, sprays, ointments, and inhalants. The active compoundmay be mixed under sterile conditions with a pharmaceutically acceptablecarrier and any needed preservatives, buffers or propellants which maybe required. Ophthalmic formulations, eye ointments, powders andsolutions are also contemplated as being within the scope of thisinvention.

Methods of Use

The compounds and compositions using any amount and any route ofadministration may be administered to a subject for the treatment orprevention of pain, substance abuse (especially in alcohol dependence),or spasticity.

The term “administering” refers to the method of contacting a compoundwith a subject. Thus, the compounds may be administered by injection,that is, intravenously, intramuscularly, intracutaneously,subcutaneously, intraduodenally, parentally, or intraperitoneally. Also,the compounds described herein may be administered by inhalation, forexample, intranasally. Additionally, the compounds may be administeredtransdermally, topically, via implantation, transdermally, topically,and via implantation. In certain embodiments, the compounds andcompositions thereof may be delivered orally. The compounds may also bedelivered rectally, bucally, intravaginally, ocularly, or byinsufflation. GABA-B modulated disorders and conditions may be treatedprophylactically, acutely, and chronically using compounds andcompositions thereof, depending on the nature of the disorder orcondition. Typically, the host or subject in each of these methods ishuman, although other mammals may also benefit from the administrationof compounds and compositions thereof as set forth hereinabove.

Compounds of the invention are useful as positive allosteric modulatorsof GABA-B. Thus, the compounds and compositions are particularly usefulfor treating or lessening the severity, or progression of a disease,disorder, or a condition where the GABA-B receptor is involved. Inparticular, the invention provides a method for treating of pain,substance abuse, especially in alcohol dependence, or spasticity in asubject, wherein the method comprises the step of administering to saidsubject a therapeutically effective amount of a compound of formula (I)or a preferred embodiment thereof as set forth above, with or without apharmaceutically acceptable carrier. Particularly, the method is for thetreatment or prevention of pain.

A compound according to formula (I) or a pharmaceutically acceptablesalt or isotopically labeled form thereof for use in therapy.

A compound according to formula (I) or a pharmaceutically acceptablesalt or isotopically labeled form thereof for use in the treatment of acondition or disorder modulated by the γ-aminobutyric acid B (GABA-B)receptor in a mammal. Preferable, the condition or disorder is selectedfrom the group consisting of pain, substance abuse, especially inalcohol dependence, spasticity, fragile X syndrome, Down's syndrome,autism, retinal ganglion cell degeneration, gastro-esophageal refluxdisease (GERD), smoking cessation, addiction of narcotic agents, emesis,cough, overactive bladder, anxiety, migraine and tinnitus.

The use of a compound according to formula (I) or a pharmaceuticallyacceptable salt or isotopically labeled form thereof for the preparationof a medicament.

The use of a compound according to formula (I) or a pharmaceuticallyacceptable salt or isotopically labeled form for the preparation of amedicament for the treatment of a condition or disorder modulated by theγ-aminobutyric acid B (GABA-B) receptor in a mammal. Preferable, theconsition or disorder is selected from the the group consisting of pain,substance abuse, especially in alcohol dependence, spasticity, fragile Xsyndrome, Down's syndrome, autism, retinal ganglion cell degeneration,gastro-esophageal reflux disease (GERD), smoking cessation, addiction ofnarcotic agents, emesis, cough, overactive bladder, anxiety, migraineand tinnitus. The medicament optionally can comprise one or moreadditional therapeutic agents.

The present compounds may be co-administered to a subject. The term“co-administered” means the administration of two or more differenttherapeutic agents that are administered to a subject by combination inthe same pharmaceutical composition or separate pharmaceuticalcompositions. Thus co-administration involves administration at the sametime of a single pharmaceutical composition comprising two or moretherapeutic agents or administration of two or more different separatecompositions to the same subject at the same or different times.

The compounds of the invention may be co-administered with atherapeutically effective amount of one or more agents to treat pain,where examples of the agents include, nonsteroidal anti-inflammatorydrugs (NSAIDs), opioid analgesics, barbiturates, benzodiazapines,histamine antagonists, sedatives, skeletal muscle relaxants, transientreceptor potential ion channel antagonists, α-adrenergics, tricyclicantidepressants, anticonvulsants, tachykinin antagonists, muscarinicantagonists, cyclooxygenase-2 selective inhibitors, neuroleptics,vanilloid receptor agonists, vanilloid receptor antagonists,β-adrenergics, local anesthetics, corticosteroids, 5-HT receptoragonists, 5-HT receptor antagonists, 5-HT_(2A) receptor antagonists,cholinergic analgesics, a₂6 ligands (such as gabapentin or pregabalin),cannabinoid receptor ligands, metabotropic glutamate subtype 1 receptorantagonists, serotonin reuptake inhibitors, norepinephrine reuptakeinhibitors, dual serotonin-noradrenaline reuptake inhibitors, Rho kinaseinhibitors, inducible nitric oxide synthase inhibitors,acetylcholinesterase inhibitors, prostaglandin E₂ subtype 4 antagonists,leukotriene B4 antagonists, 5-lipoxygenase inhibitors, sodium channelblockers, 5-HT₃ antagonists, N-methyl-D-aspartic acid receptorantagonists, phosphodiesterase V inhibitors, voltage-gated calciumchannel blockers (e.g., N-type and T-type), and KCNQ openers (e.g.,KCNQ2/3 (K_(v)7.2/3)).

This invention also is directed to kits that comprise one or morecompounds and/or salts of the invention, and, optionally, one or moreadditional therapeutic agents.

This invention also is directed to methods of use of the compounds,salts, compositions, and/or kits of the invention to, for example,modulate the γ-aminobutyric acid receptor, and treat a disease treatableby modulating the γ-aminobutyric acid receptor, including pain,substance abuse, especially in alcohol dependence, spasticity, fragile Xsyndrome, Down's syndrome, autism, retinal ganglion cell degeneration,gastro-esophageal reflux disease (GERD), smoking cessation, addiction ofnarcotic agents, emesis, cough, overactive bladder, anxiety, migraine ortinnitus.

This invention also is directed to a use of one or more compounds orsalts or isotopically labeled forms thereof of the invention in thepreparation of a medicament. The medicament optionally can comprise oneor more additional therapeutic agents. In some embodiments, themedicament is useful for treating pain, substance abuse (especially inalcohol dependence), spasticity, fragile X syndrome, Down's syndrome,autism, retinal ganglion cell degeneration, gastro-esophageal refluxdisease (GERD), smoking cessation, addiction of narcotic agents, emesis,cough, overactive bladder, anxiety, migraine or tinnitus.

Further benefits of Applicants' invention will be apparent to oneskilled in the art from reading this patent application.

The following Examples may be used for illustrative purposes and shouldnot be deemed to narrow the scope of the invention.

EXAMPLES

Abbreviations: d for day; h for hour; dppf for1,1′-bis(diphenylphosphino)ferrocene, DCM for dichloromethane, DMF forN,N-dimethyl formamide, DMSO for dimethyl sulfoxide; ee for enantiomericexcess; ESI for electrospray ionization; Et for ethyl; EtOAc for ethylacetate; HPLC for high performance liquid chromatography; MTBE formethyl-t-butyl ether, MS for mass spectrometry, LC-MS for liquidchromatography/mass spectrometry; PE for petroleum ether; psi for poundsper square inch; TFA for trifluoroacetic acid; THF for tetrahydrofurate,TLC for thin layer chromatography, and room temperature (20-25° C.); APIand APCI for atmospheric pressure (chemical) ionization; SFC forsupercritical fluid chromatography.

In the context of NMR spectroscopy the following appreviations are used:s for singlet; d for doublet; t for triplet; dd for doublet of doublet;m for multiplet.

Liquid Chromatography Conditions for Liquid Chromatography-MassSpectrometry:

Method A: The gradient was 10-90% B in 1.15 minutes with a hold at 90% Bfor 0.40 minute, 90-10% B in 0.01 minute, and then hold at 10% B for0.54 minute (1.0 mL/minute flow rate). Mobile phase A was 0.0375%trifluoroacetic acid in water, mobile phase B was 0.018% trifluoroaceticacid in acetonitrile. The column used for the chromatography was a2.1×30 mm Halo® C18 column (2.7 μm particles). Detection methods werediode array (DAD) and positive/negative electrospray ionization (ESI).

Method B: The gradient was 10-100% B in 3.4 minutes with a hold at 100%B for 0.45 minute, 100-10% B in 0.01 minute, and then hold at 10% B for0.65 minute (0.8 mL/minute flow rate). Mobile phase A was 0.0375%trifluoroacetic acid in water, mobile phase B was 0.018% trifluoroaceticacid in acetonitrile. The column used for the chromatography was a2.1×50 mm Bonna-Agela Venusil® XBP-C18 HPLC column (5 μm particles).Detection methods were diode array (DAD) and evaporative lightscattering (ELSD) detection as well as positive/negative electrosprayionization (ESI).

Method C: The gradient was 1-90% B in 3.4 minutes, 90-100% B for 0.45minute, 100-1% B in 0.01 minute, and then hold at 1% B for 0.65 minute(0.8 mL/minute flow rate). Mobile phase A was 0.0375% trifluoroaceticacid in water, mobile phase B was 0.018% trifluoroacetic acid inacetonitrile. The column used for the chromatography was a 2.1×50 mmBonna-Agela Venusil® XBP-C18 column HPLC (5 μm particles). Detectionmethods were diode array (DAD) and evaporative light scattering (ELSD)detection as well as positive/negative electrospray ionization (ESI).

Method D: The gradient was 25-100% B in 3.4 minutes with a hold at 100%B for 0.45 minute, 100-25% B in 0.01 minute, and then held at 25% B for0.65 minute (0.8 mL/min flow rate). Mobile phase A was 0.0375%trifluoroacetic acid in water, mobile phase B was 0.018% trifluoroaceticacid in HPLC grade acetonitrile. The column used for the chromatographywas a 2.0×50 mm Phenomenex® Synergi™ Polar-RP column (4 μm particles).Detection methods were diode array (DAD) and evaporative lightscattering (ELSD) detection as well as positive/negative electrosprayionization (ESI).

Method E: The gradient was 40-100% B in 3.4 minutes, with a hold at 100%B for 0.45 minute, 100-40% B in 0.01 minute, and then held at 40% B for0.65 minute (0.8 mL/min flow rate). Mobile phase A was 0.0375%trifluoroacetic acid in water, mobile phase B was 0.018% trifluoroaceticacid in acetonitrile. The column used for the chromatography was aPhenomenex® Luna® C18(2) (5 μm particle size, 100 Å pore size).Detection methods are diode array (DAD) and evaporative light scattering(ELSD) detection as well as positive/negative electrospray ionization(ESI).

Method F: The gradient was 25-100% B in 3.4 minutes, 100% B for 0.45minute, 100-25% B in 0.01 minute, and then hold at 25% B for 0.65 minute(0.8 mL/minute flow rate). Mobile phase A was 0.0375% trifluoroaceticacid in water, mobile phase B was 0.018% trifluoroacetic acid inacetonitrile. The column used for the chromatography was a 2.1×50 mmBonna-Agela Venusil® XBP-C18 HPLC column (5 μm particles). Detectionmethods were diode array (DAD) and evaporative light scattering (ELSD)detection as well as positive/negative electrospray ionization (ESI).

Preparative Liquid Chromatography Conditions

Method A: Phenomenex® Luna® C18 250×50 mm (10 μm) column. Mobile phaseA—water with 0.09% trifluoroacetic acid, Mobile phase B—acetonitrile.Gradient—35-65% B over 20 minutes. Flow rate—80 mL/minute. Injectionamount—0.7 g per injection.

Method B: Bonna-Agela C18 130×25 mm HPLC column. Mobile phase A—waterwith 0.075% trifluoroacetic acid, Mobile phase B—methanol.Gradient—58-88% B over 12 minutes, hold for 2 minutes, 88-100% B over0.2 minutes, hold for 2 minutes, 100-58% B over 0.2 minutes, hold for1.6 minutes. Flow rate—25 mL/minute. Detection at 220 and 254 nm.

Method C: Samples were purified by preparative HPLC using a WatersSunfire™ C8(2) 5 μm column (30 mm×150 mm) at ambient temperature. Agradient of acetonitrile (A) and 0.1% trifluoroacetic acid in water (B)was used, at a flow rate of 50 mL/minute (0-1.0 minute 5% A, 0.5-8.5minutes linear gradient % A defined in experimental, 8.7-10.7 minutes100% A, 10.7-11 minutes linear gradient 100-5% A). Samples were injectedin 1.5 mL dimethyl sulfoxide:methanol (1:1). An Agilent® 1100 SeriesPurification system was used, consisting of the following modules:Agilent® 1100 Series LC/MSD SL mass spectrometer with API—electrospraysource; two Agilent® 1100 Series preparative pumps; Agilent 1100 Seriesisocratic pump; Agilent® 1100 Series diode array detector withpreparative (0.3 mm) flow cell; Agilent® active-splitter; and IFC-PALfraction collector/autosampler. The make-up pump for the massspectrometer used 3:1 methanol:water with 0.1% formic acid at a flowrate of 1 mL/minute. Fraction collection was automatically triggeredwhen the extracted ion chromatogram (EIC) for the target mass exceededthe threshold specified in the method. The system was controlled usingAgilent® Chemstation (Rev B.10.03), Agilent® A2Prep, and Leap FractPalsoftware, with custom Chemstation® macros for data export.

Method D: Column: Waters Xbridge™ C18, 19×150 mm, 5 μm column. Eluent:Mobile phase A—water/0.05% trifluoroacetic acid; Mobile phaseB—acetonitrile; flow rate—20 mL/minute; gradient—30-70% B in 10 minutes.Detection: 254 nm.

Method E: Column: Waters Xbridge™ C18, 19×150 mm, 5 μm column. Eluent:Mobile phase A—water/10 mM NH₄CO₃; Mobile phase B—acetonitrile; flowrate—20 mL/minute; gradient—30-70% B in 10 minutes. Detection: 254 nm.

Method F: Samples were purified by preparative HPLC using two coupledPhenomenex® Luna® Axia™ C8, 5 μm columns (30 mm×150 mm, each) at ambienttemperature. A gradient of acetonitrile (A) and 0.1% trifluoroaceticacid in water (B) was used, at a flow rate of 50 mL/minute (0-0.5 minute5% A, 0.5-8.5 minutes linear gradient % A defined in experimental,8.7-10.7 minutes 100% A, 10.7-11 minutes linear gradient 100-5% A).Samples were injected in 1.5 mL dimethyl sulfoxide:methanol (1:1). AnAgilent 1100 Series Purification system was used, consisting of thefollowing modules: Agilent 1100 Series LC/MSD SL mass spectrometer withAPI-electrospray source; two Agilent 1100 Series preparative pumps;Agilent 1100 Series isocratic pump; Agilent 1100 Series diode arraydetector with preparative (0.3 mm) flow cell; Agilent active-splitter;and IFC-PAL fraction collector/autosampler. The make-up pump for themass spectrometer used 3:1 methanol:water with 0.1% formic acid at aflow rate of 1 mL/minute. Fraction collection was automaticallytriggered when the extracted ion chromatogram (EIC) for the target massexceeded the threshold specified in the method. The system wascontrolled using Agilent Chemstation (Rev B.10.03), Agilent A2Prep, andLeap FractPal software, with custom Chemstation macros for data export.

Preparative Super Critical Fluid Chromatography Conditions

Method A: Thar SFC Prep-80. Column—Daicel Chiralcel® OD-H (5 μm) 3.0×25cm. Mobile phase A—CO₂, Mobile phase B—2-propanol (0.05% NH₄OH).Gradient A:B, 65:35. Flow rate—70 mL/minute. System back pressure—100bar. Detection wavelength—220 nm. Sample preparation: 10 mg/mL inmethanol and dichloromethane. Injection—1 mL/injection.

Method B: Thar SFC Prep-80. Column—Daicel Chiralcel® OJ-H (5 μm) 3.0×25cm. Mobile phase A—CO₂, Mobile phase B—methanol (0.05% NH₄OH). GradientA:B, 75:25. Flow rate—65 mL/minute. System back pressure—100 bar.Detection wavelength—220 nm. Sample preparation: 25 mg/mL in methanol.Injection—1 mL/injection.

Example 1N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide

Step 17-bromo-5-(1-(4-chlorophenyl)ethyl)-3-cyclopropylisoxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-3-cyclopropylisoxazolo[4,5-d]pyridazin-4(5H)-one (Example 51,600 mg, 2.343 mmol) in N,N-dimethylformamide (10 mL) K₂CO₃ (1295 mg,9.37 mmol) and 1-(1-bromoethyl)-4-chlorobenzene (772 mg, 3.51 mmol) wereadded. After stirring at 20° C. for 2 hrs, the mixture was diluted withwater, extracted with EtOAc (20 ml, 3 times). The organic phase waswashed with brine, concentrated under reduced pressure to get a residue,which was washed with MeOH, dried to give crude7-bromo-5-(1-(4-chlorophenyl)ethyl)-3-cyclopropylisoxazolo[4,5-d]pyridazin-4(5H)-one(560 mg, 1.419 mmol, 60.6% yield) as a white solid, which was useddirectly for next step. ¹H NMR (400 MHz, DMSO-d6) δ ppm 7.39 (s, 4H),7.17-7.08 (m, 2H), 6.92 (d, J=2.6 Hz, 1H), 6.30 (q, J=7.1 Hz, 1H), 3.71(d, J=7.1 Hz, 6H), 2.46-2.39 (m, 1H), 1.71 (d, J=7.1 Hz, 3H), 1.14 (d,J=7.5 Hz, 4H).

Step 2N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl(acetamide)

To a solution of7-bromo-5-(1-(4-chlorophenyl)ethyl)-3-cyclopropylisoxazolo-[4,5-d]pyridazin-4(5H)-one(270 mg, 0.684 mmol) in N,N-dimethylformamide (Ratio: 4.00, Volume: 2ml) and water (Ratio: 1.000, Volume: 0.5 ml)(5-acetamido-2-methoxyphenyl)boronic acid (172 mg, 0.821 mmol),monopotassium monocarbonate (170 mg, 1.710 mmol) and Pd(Ph₃P)₄ (79 mg,0.068 mmol) were added. After stirring at 80° C. overnight, the mixturewas diluted with water, extracted with EtOAc (100 ml, 3 times). Theorganic phase was washed with brine, concentrated under reducedpressure. The residue was purified by preparative HPLC (Gilson 281 semipreparative HPLC system, mobile phase: A: TFA/H₂O=0.075% v/v, B:acetonitrile (57%->100%), column: YMC-Actus®, ODS-AQ 100*30 5u, flowrate: 25 ml/min, monitor wavelenth: 220&254 nm).

The enantiomers ofN-(3-{5-[1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamidewere separated by supercritical fluid chromatography to give the titledcompound. The mobile phase was comprised of supercritical CO₂ suppliedby a bulk tank of 99.5% bone-dry non-certified CO₂ pressurized to 1200psi (82.7 bar) with a modifier of methanol (0.1 N NH₄OH) at a flow rateof 60 g/minute. UV detection was set to collect at a wavelength of 220nm, the column was heated to 35° C., and the backpressure regulator wasset to maintain 100 bar. The sample was dissolved in methanol at aconcentration of about 50 mg/mL, and the injection volume was 1 mL. Themobile phase was held isocratically at 35% methanol (0.1 N NH₄OH):CO2.The instrument was fitted with a Chiralcel® OJ-H, 5 μm, 3.0 cm id×25 cmL column. ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.96 (s, 1H), 7.72-7.67 (m,2H), 7.39 (s, 4H), 7.17-7.13 (m, 1H), 6.31 (q, J=6.8 Hz, 1H), 3.72 (s,3H), 2.45-2.39 (m, 1H), 2.02 (s, 3H), 1.71 (d, J=7.1 Hz, 3H), 1.17-1.11(m, 4H).

Example 25-(4-chlorobenzyl)-7-(4-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-oneStep 1: ethyl 2-methyl-4-oxo-4,5-dihydrofuran-3-carboxylate

To an ice bath cooled solution of magnesiumethanolate (31.7 g, 277 mmol)in toluene (54 mL) was added ethyl acetoacetate (30 g, 231 mmol)dropwise. The mixture was stirred at room temperature for 1 hour.Anhydrous acetonitrile (54 mL) was added to the mixture at −10° C.,followed by the slow addition of 2-chloroacetyl chloride (26.0 g, 231mmol). The mixture was allowed to warm to room temperature and left tostir for 2 hours. A dilute solution of sulfuric acid (8 mL acid in 280mL ice/water) was added, followed by extraction with tert-butyl methylether. The combined organic fractions were dried over Na₂SO₄ andfiltered, and the filtrate was cooled to 0° C. A solution oftriethylamine (23.33 g, 231 mmol) in tert-butylmethyl ether (50 mL) wasadded. The reaction mixture was left to stir at room temperatureovernight. The mixture was diluted with water, and extracted withdichloromethane. The organic phase was concentrated under reducedpressure to give a residue that was purified by chromatography on silicagel and eluted with EtOAc/PE to give the titled compound (16 g, yield40%). ¹H NMR (400 MHz, CDCl₃) δ ppm 4.59 (s, 2H), 4.31 (q, J=7.06 Hz,2H), 2.61 (s, 3H), 1.33-1.37 (m, 3H).

Step 2: ethyl 5-(hydroxymethyl)-3-methyl-1,2-oxazole-4-carboxylate

To a solution of ethyl 2-methyl-4-oxo-4,5-dihydrofuran-3-carboxylate (20g, 118 mmol, Step 1) in anhydrous ethanol (100 mL) was added sodiumacetate (9.64 g, 118 mmol) and hydroxylamine (8.17 g, 118 mmol). Themixture was heated to reflux for 1 hour. The solvent was removed underreduced pressure to give a residue that was diluted with water andextracted with ethyl acetate. The organic phase was washed with brine,dried over Na₂SO₄, and concentrated under reduced pressure to get aresidue that was purified by chromatography on silica gel and elutedwith EtOAc/PE to give the titled compound (12 g, yield 55%). ¹H NMR (400MHz, CDCl₃) δ ppm 4.89 (d, J=6.62 Hz, 2H), 4.38 (q, J=7.06 Hz, 2H), 3.97(t, J=7.06 Hz, 1H), 2.46 (s, 3H), 1.41 (t, J=7.06 Hz, 3H).

Step 3: ethyl 5-formyl-3-methyl-1,2-oxazole-4-carboxylate

To a solution of ethyl5-(hydroxymethyl)-3-methyl-1,2-oxazole-4-carboxylate (30 g, 162 mmol,Step 2) in anhydrous toluene (500 mL) was added manganese(IV) oxide(42.3 g, 486 mmol). The mixture was heated to reflux for 6 hours. Thesolids were removed by filtration, and the filtrate was concentratedunder reduced pressure to give a residue that was purified bychromatography on silica gel and eluted with EtOAc PE to give the titledcompound (13 g, yield 43%). ¹H NMR (400 MHz, CDCl₃) δ ppm 10.35 (s, 1H),4.38-4.51 (m, 2H), 2.55 (s, 3H), 1.39-1.44 (m, 3H).

Step 4: 3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of ethyl 5-formyl-3-methyl-1,2-oxazole-4-carboxylate (13g, 71.0 mmol, Step 3) in ethanol (60 mL) chilled in an ice-bath wasadded hydrazine hydrate (17.7 g, 355 mmol) dropwise. The resultingmixture was stirred for 2 hours. The solid was collected by filtrationand dried to give the titled compound (10 g, yield 93%). ¹H NMR (400MHz, methol-d₄) δ ppm 8.48 (s, 1H), 2.62 (s, 3H).

Step 5: 7-bromo-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (10 g,66.2 mmol, Step 4) in CH₃OH (600 mL) chilled in an ice-water bath wasadded lithium hydroxide hydrate (22.21 g, 529 mmol) and Br₂ (0.387 mL,7.51 mmol) dropwise. The mixture was heated to reflux overnight. Themixture was diluted with water and extracted with ethyl acetate. Theorganic phase was washed with brine, dried over Na₂SO₄, and concentratedunder reduced pressure. The resultant residue was purified bychromatography on silica gel and eluted with EtOAc/PE to give the titledcompound (12 g, yield 79%). ¹H NMR (400 MHz, CDCl₃) δ ppm 11.37 (br,1H), 2.63 (s, 3H).

Step 6:7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 7-bromo-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(8 g, 34.8 mmol, Step 5) in N,N-dimethylformamide (200 mL) was addedK₂CO₃ (9.61 g, 69.6 mmol) at room temperature.1-Chloro-4-(chloromethyl)benzene (8.4 g, 52.2 mmol) was added in oneportion. The mixture was stirred at room temperature for 4 hours. Themixture was diluted with water and extracted with ethyl acetate. Theorganic phase was washed with brine and concentrated under reducedpressure to give a residue that was washed with CH₃OH to give the titledcompound (12 g, yield 97%) as a solid. LCMS (ESI+) m/z 354 (M+H)⁺,retention time 3.322 minutes; ¹H NMR (400 MHz, CDCl₃) δ ppm 7.37-7.47(m, 2H), 7.28-7.36 (m, 2H), 5.33 (s, 2H), 2.67 (s, 3H).

Step 7:5-(4-chlorobenzyl)-7-(4-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Step 6) in 1,2-dimethoxyethane (4 mL) and water (1mL) was added (4-methoxyphenyl)boronic acid (51.4 mg, 0.338 mmol), K₂CO₃(0.097 g, 0.705 mmol) and tetrakis(triphenylphosphine)palladium(0)(0.033 g, 0.028 mmol). The resulting mixture was stirred at 80° C.overnight under N₂. After cooling down to room temperature, the reactionmixture was concentrated under reduced pressure to furnish a residuewhich was washed with a mixture of CH₃OH and H₂O to give the titledcompound. LCMS (ESI+) m/z 381 (M+H)⁺; ¹H NMR (CDCl₃, 400 MHz):δ 8.09 (d,J=8.82 Hz, 2H), 7.44 (d, J=8.38 Hz, 2H), 7.30 (d, J=8.38 Hz, 2H), 7.04(d, J=8.82 Hz, 2H), 5.41 (s, 2H), 3.89 (s, 3H), 2.70 (s, 3H).

Example 3N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide

The enantiomers ofN-(3-{5-[1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide(see Example 1) were separated by supercritical fluid chromatography togive the titled compound. The mobile phase was comprised ofsupercritical CO₂ supplied by a bulk tank of 99.5% bone-drynon-certified CO₂ pressurized to 1200 psi (82.7 bar) with a modifier ofmethanol (0.1 N NH₄OH) at a flow rate of 60 g/minute. UV detection wasset to collect at a wavelength of 220 nm, the column was heated to 35°C., and the backpressure regulator was set to maintain 100 bar. Thesample was dissolved in methanol at a concentration of about 50 mg/mL,and the injection volume was 1 mL. The mobile phase was heldisocratically at 35% methanol (0.1 N NH₄OH):CO2. The instrument wasfitted with a Chiralcel® OJ-H, 5 μm, 3.0 cm id×25 cm L column. ¹H NMR(400 MHz, DMSO-d₆) δ ppm 9.96 (s, 1H), 7.72-7.67 (m, 2H), 7.39 (s, 4H),7.17-7.13 (m, 1H), 6.31 (q, J=6.8 Hz, 1H), 3.72 (s, 3H), 2.45-2.39 (m,1H), 2.02 (s, 3H), 1.71 (d, J=7.1 Hz, 3H), 1.17-1.11 (m, 4H).

Example 45-[1-(4-chlorophenyl)ethyl]-7-(2,6-difluoropyridin-4-yl)-3-methyl[1,2]oxazole[4,5-d]pyridazin-4(5H)-one

A microwave vial was charged with SiliaCat® DPP-Pd(diphenylphosphinepalladium (II)) (32 mg, 0.5 mmol/g) and K₂CO₃ (34 mg). Then a solutionof7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(30 mg, 0.08 mmol, Example 39-Step 5) dissolved in1,2-dimethoxyethane:water (4:1, 1.0 mL) was added, followed by(2,6-difluoropyridin-4-yl)boronic acid (25 mg, 0.16 mmol) dissolved in1,2-dimethoxyethane:water (4:1, 0.3 mL). The resulting mixture washeated and stirred at 80° C. overnight. The reaction mixture wasfiltered and purified by preparative liquid chromatography (Method C,0.5-8.5 minutes linear gradient 55-90% A) to provide the titledcompound. ¹H NMR (400 MHz,DMSO-d₆/D₂O, Temperature=90° C.) δ ppm 7.64(s, 2H), 7.47-7.44 (m, 2H), 7.40-7.36 (m, 2H), 6.33 (q, J=6.4, 5.8 Hz,1H), 2.62 (s, 3H), 1.84 (d, J=7.0 Hz, 3H).

Example 57-(2,4-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-oneStep 1:7-(2,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a mixture of 7-bromo-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(1 g, 4.3 mmol, Example 2-Step 5) and (2,4-dimethoxyphenyl)boronic acid(1.02 g, 8.6 mmol) in 1,2-dimethoxyethane (20 mL) and H₂O (5 mL) wasadded K₂CO₃ (1.5 g, 10.9 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.5 g, 0.4 mmol). Theresulting mixture was stirred at 100° C. under N₂ overnight. Aftercooling to room temperature, the mixture was concentrated under reducedpressure. Water and methanol (20 ml, 1:1) were added to the residue, andthe mixture was stirred for 10 minutes. The precipitate was collected byfiltration and dried to afford the titled compound.

Step 2:7-(2,4-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-(2,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg,) and K₂CO₃ (2.0 eq) in N,N-dimethylformamide (2 mL) was added4-(bromomethyl)pyridine (1.1 eq), and the mixture was stirred at roomtemperature overnight. Water was added, and the mixture was extractedwith ethyl acetate. The combined organic phase was concentrated underreduced pressure, and the residue was purified by preparative HPLC(method C) to give the titled compound.

Example 67-(2-amino-5-chlorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-oneStep 1: methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate

To a solution of methyl 2-bromo-4-chlorophenylcarbamate (44 g, 166mmol), 4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-bi(1,3,2-dioxaborolane) (54.9g, 216 mmol) and potassium acetate (40.8 g, 416 mmol) in 1,4-dioxane wasadded [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (6.09g, 8.32 mmol, Pd(dppf)Cl₂). The mixture was stirred as 80° C. for 14hours and then concentrated under reduced pressure. The residue wasdissolved in ethyl acetate (100 mL) and extracted with brine (3×50 mL).The organic fraction was dried over sodium sulfate and concentratedunder reduced pressure. The residue was purified by flash chromatographyto give the titled compound.

Step 2:7-(2-amino-5-chlorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.163 mmol, Example 39-Step 5) was combined with potassiumcarbonate (56.2 mg, 0.407 mmol) and methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate(50.7 mg, 0.163 mmol) in 1,2-dimethoxyethane and water (5 mL, 4:1). Thentetrakis(triphenylphosphine)palladium(0) (18.81 mg, 0.016 mmol) wasadded, and the mixture was heated for 4 hours at 80° C. under an argonatmosphere. The reaction mixture was partitioned between water and ethylacetate. The organic fraction was then washed with brine, dried overMgSO₄, and concentrated under reduced pressure. The residue waschromatographed on silica gel eluted with 30% ethyl acetate/cyclohexane.The residue was taken into a small amount of isopropanol and treatedwith HCl in isopropanol. This mixture was diluted with diisopropyl etherto precipitate the hydrochloric acid salt. The solid was collected byfiltration and dried in a vacuum oven to give the titled compound as ahydrochloride salt. ¹H NMR (600 MHz, DMSO-d₆) δ ppm 7.66 (d, J=2.4 Hz,OH), 7.45-7.37 (m, 3H), 7.22 (dd, J=8.8, 2.5 Hz, 1H), 6.82 (d, J=8.7 Hz,1H), 6.37 (q, J=6.9 Hz, 1H), 2.62 (s, 3H), 1.74 (d, J=7.0 Hz, 3H), 1.04(d, J=6.0 Hz, 1H); MS (ESI+) m/z 415.0 (M+H)⁺.

Example 75-[1-(4-chlorophenyl)ethyl]-7-(2-chloropyridin-3-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.163 mmol, Example 39-Step 5) was combined with potassiumcarbonate (56.2 mg, 0.407 mmol) and (2-chloropyridin-3-yl)boronic acid(30.7 mg, 0.195 mmol) in 1,2-dimethoxyethane and water (5 mL, 4:1). Thentetrakis(triphenylphosphine)palladium(0) (18.81 mg, 0.016 mmol) wasadded, and the mixture was heated for 4 hours at 80° C. under an argonatmosphere. The reaction mixture was partitioned between water and ethylacetate. The organic fraction was then washed with brine, dried overMgSO₄, and concentrated under reduced pressure. The residue was purifiedby flash chromatography using a Teledyne Isco CombiFlash® Rf apparatuswith a 4 g silica gel cartridge eluted with 30% ethylacetate/cyclohexane. The product containing fractions were combined andconcentrated. The residue was dried in a vacuum oven overnight to givethe titled compound. ¹H NMR (600 MHz, DMSO-d₆) δ ppm 8.64 (dd, J=4.8,1.9 Hz, 1H), 8.18 (dd, J=7.6, 1.9 Hz, 1H), 7.69 (dd, J=7.6, 4.8 Hz, 1H),7.41 (s, 3H), 6.33 (q, J=7.0 Hz, 1H), 2.61 (s, 3H), 1.74 (d, J=7.0 Hz,3H), 1.40 (s, 5H); MS (ESI+) m/z 401.0 (M+H)⁺.

Example 8N-{5-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-2-fluorophenyl}acetamideStep 1:N-[2-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]acetamide

To a solution of N-(5-bromo-2-fluorophenyl)acetamide (6 g, 25.9 mmol) in1,4-dioxane (100 mL) was added K₂CO₃ (7.61 g, 78 mmol),bis(pinacolato)diboron (7.88 g, 31 mmol) and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.946 g,1.29 mmol, Pd(dppf)Cl₂). The resulting mixture was heated to refluxunder N₂ overnight. The reaction was diluted with water and extractedwith ethyl acetate. The organic phase was washed with brine,concentrated under reduced pressure to give a residue that was purifiedby column chromatography on silica gel and eluted with EtOAc/PE to givethe titled compound (6 g, yield 83%). ¹H NMR (400 MHz, CDCl₃) δ ppm 8.62(d, J=7.94 Hz, 1H), 7.53 (t, J=6.62 Hz, 1H), 7.28 (s, 1H), 7.09 (dd,J=11.03 Hz, 8.38 Hz, 1H), 2.23 (s, 3H), 1.34 (s, 12H).

Step 2:N-{5-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-2-fluorophenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(120 mg, 0.338 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was addedN-[2-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]acetamide(113 mg, 0.406 mmol, Step 1), K₂CO₃ (117 mg, 0.846 mmol) andtetrakis(triphenylphosphine)palladium(0) (39.1 mg, 0.034 mmol). Theresulting mixture was stirred at 80° C. under N₂ overnight. The mixturewas diluted with water and extracted with ethyl acetate. The organicphase was washed with brine and concentrated under reduced pressure togive a residue that was purified by preparative HPLC (method B) tosupply the titled compound (70 mg, yield 50%). LCMS (ESI+) m/z427(M+H)⁺, retention time 3.325 minutes; ¹H NMR (400 MHz, CDCl₃) δ ppm9.15 (d, J=6.62 Hz, 1H), 7.89 (br, s, 1H), 7.37-7.55 (m, 3H), 7.34 (d,J=8.38 Hz, 2H), 7.23-7.27 (m, 1H), 5.46 (s, 2H), 2.73 (s, 3H), 2.31 (s,3H).

Example 97-(2,5-dimethoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2,5-dimethoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. ¹H NMR (400 MHz, CD₃OD): δ7.71-7.68(m, 2H), 7.17-7.11 (m, 3H), 6.99 (s, 2H), 5.43 (s, 2H), 3.88 (s, 3H),3.80 (s, 3H), 3.77 (s, 3H), 2.63 (s, 3H); m/z 476.0 (M+H)⁺

Example 105-[2-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-oneStep 1:7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

Under argon, 7-bromo-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (100mg, 0.435 mmol, Example 2-Step 5) was suspended in toluene and methanol(3 mL, 1:1). 2 M Aqueous sodium bicarbonate (0.326 mL, 0.652 mmol) and(2,5-dimethoxyphenyl)boronic acid (79 mg, 0.435 mmol) were addedfollowed by tetrakis(triphenylphosphine)palladium(0) (50.2 mg, 0.043mmol). The reaction mixture was heated with stirring in a Biotage®microwave reactor at 120° C. for 30 minutes. The reaction mixture wasthen partitioned between water and ethyl acetate. The aqueous phase wasextracted twice more with ethyl acetate. The combined organic fractionswere dried over MgSO₄ and then concentrated under reduced pressure. Theresidue was purified by flash chromatography on a Teledyne IscoCombiFlash® Companion® apparatus using a RediSep® silica gel cartridge(4 g) eluted with 10% methanol/dichloromethane. MS (ESI+) m/z 288.1(M+H)⁺.

Step 2:5-[2-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-(2,5-Dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(50 mg, 0.174 mmol) was dissolved in N,N-dimethylformamide (5 mL), andthe resultant solution was cooled to 0° C.1-(2-Bromoethyl)-4-chlorobenzene (57.3 mg, 0.261 mmol) and potassiumcarbonate (60.1 mg, 0.435 mmol) were added. The reaction mixture wasallowed to warm to room temperature and was stirred overnight. Thereaction mixture was partitioned between ethyl acetate and water. Theaqueous phase was extracted twice more with ethyl acetate. The combinedorganic fractions were washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® Companion® apparatus usinga RediSep® silica gel cartridge (4 g) eluted with 10%methanol/dichloromethane. The solid was triturated with a little ethylacetate/heptane (1:1), and the precipitate was collected by vacuumfiltration. The solid was dried in a vacuum oven to give the titledcompound. ¹H NMR (600 MHz, DMSO-d₆) δ ppm 7.36-7.31 (m, 2H), 7.26-7.21(m, 2H), 7.18-7.09 (m, 2H), 6.75 (d, J=3.1 Hz, 1H), 4.43 (t, J=7.1 Hz,2H), 3.73 (d, J=12.8 Hz, 6H), 3.32 (s, OH), 3.08 (t, J=7.1 Hz, 2H), 2.60(s, 3H); MS (ESI+) m/z 426.1 (M+H)⁺.

Example 117-[2-amino-5-(trifluoromethyl)phenyl]-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg, 0.217 mmol, Example 39-Step 5) in ethanol/toluene (1:1, 2 mL)was combined with 2 M aqueous sodium carbonate (0.163 mL, 0.326 mmol)and2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4-(trifluoromethyl)aniline(62.3 mg, 0.217 mmol). Then tetrakis(triphenylphosphine)palladium(0)(25.08 mg, 0.022 mmol) was added, and the mixture was heated in a CEMmicrowave reactor for 30 minutes at 130° C. under an argon atmosphere.The reaction mixture was partitioned between water and ethyl acetate.The organic fraction was then washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® Rf apparatus using asilica gel cartridge (4 g) eluted with ethyl acetate/cyclohexane. Asecond flash chromatography on a Teledyne Isco CombiFlash® Rf apparatususing a silica gel cartridge (4 g, 15 μm) eluted with 30% ethylacetate/cyclohexane provided the titled compound which was driedovernight in a vacuum oven. ¹H NMR (600 MHz, DMSO-d₆) δ ppm 7.53 (d,J=8.7 Hz, 1H), 7.41-7.31 (m, 4H), 6.83-6.74 (m, 2H), 6.30 (q, J=7.1 Hz,1H), 6.17 (s, 2H), 3.35-3.29 (m, 1H), 2.59 (s, 3H), 1.68 (d, J=7.0 Hz,3H), 1.40 (s, 2H); MS (ESI+) m/z 449.1 (M+H)⁺.

Example 125-[1-(4-chlorophenyl)ethyl]-7-(1H-indol-6-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.163 mmol, Example 39-Step 5) in 1,2-dimethoxyethane/water(4:1, 5 mL) was combined with potassium carbonate (56.2 mg, 0.407 mmol)and (1H-indol-6-yl)boronic acid (31.4 mg, 0.195 mmol). Thentetrakis(triphenylphosphine)palladium(0) (18.81 mg, 0.016 mmol) wasadded, and the mixture was heated for 4 hours at 80° C. under an argonatmosphere. The reaction mixture was partitioned between water and ethylacetate. The organic fraction was then washed with brine, dried overMgSO₄, and concentrated under reduced pressure. The residue was purifiedby flash chromatography on a Teledyne Isco CombiFlash® Rf apparatususing a silica gel cartridge (4 g) eluted with 30% ethylacetate/cyclohexane. The residue was triturated with a little ethylacetate/diisopropyl ether. The solid was collected by vacuum filtrationand dried overnight in a vacuum oven to give the titled compound. ¹H NMR(600 MHz, DMSO-d₆) δ ppm 11.45 (s, 1H), 7.77 (dd, J=7.4, 0.9 Hz, 1H),7.60 (dt, J=8.1, 1.0 Hz, 1H), 7.45 (t, J=2.8 Hz, 1H), 7.41 (s, 4H),7.32-7.25 (m, 1H), 6.66 (ddd, J=3.0, 2.1, 0.9 Hz, 1H), 6.44 (q, J=7.0Hz, 1H), 2.64 (s, 3H), 1.85 (d, J=7.0 Hz, 3H); MS (ESI+) m/z 405.1(M+H)⁺.

Example 135-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(280 mg, 0.73 mmol, Example 98-Step 6) in N,N-dimethylformamide (2 mL)and water (0.5 mL) was added (2,5-dimethoxyphenyl)boronic acid (134 mg,0.73 mmol), K₂CO₃ (202 mg, 1.47 mmol) andtetrakis(triphenylphosphine)palladium(0) (30 mg, 0.037 mmol). Afterstirring at 80° C. overnight under nitrogen, the mixture was dilutedwith water and extracted with ethyl acetate. The organic phase waswashed with brine and concentrated under reduced pressure to give aresidue that was purified by preparative HPLC (method C) to give thetitled compound (72 mg, yield 22%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.46(d, J=8.4 Hz, 2H), 7.31 (d, J=8.4 Hz, 2H), 7.07-6.97 (m, 3H), 5.42 (s,2H), 3.82 (d, J=1.8 Hz, 6H), 3.59-3.48 (m, 1H), 1.47 (d, J=7.1 Hz, 6H);LCMS (method B) (ESI+) m/z 439.1 (M+H)⁺, retention time 3.031 minutes.

Example 147-(2-aminophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline for methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® Rf apparatus using asilica gel cartridge (4 g) eluted with 40% ethyl acetate/cyclohexane. Asecond flash chromatography on a Teledyne Isco CombiFlash® Rf apparatususing a silica gel cartridge (4 g) eluted with 2%methanol/dichloromethane. The residue was triturated with a little ethylacetate/diisopropyl ether (1:1). The residue was dried overnight in avacuum oven to give the titled compound. ¹H NMR (600 MHz, DMSO-d₆) δ ppm7.67 (dd, J=7.9, 1.5 Hz, 1H), 7.44-7.37 (m, 4H), 7.18 (ddd, J=8.6, 7.1,1.6 Hz, 1H), 6.80 (dd, J=8.3, 1.2 Hz, 1H), 6.69 (ddd, J=8.1, 7.1, 1.2Hz, 1H), 6.38 (q, J=7.0 Hz, 1H), 5.84 (s, 2H), 5.76 (s, 1H), 2.62 (s,3H), 1.75 (d, J=7.0 Hz, 3H).

Example 15N-(3-{5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamidophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 46%.

1H NMR (400 MHz, DMSO): δ 10.19 (br, 1H), 8.31 (s, 1H), 7.77-7.40 (m,5H), 7.23 (s, 1H), 5.41 (s, 2H), 3.84 (s, 3H), 2.59 (s, 3H), 2.06 (s,3H). +) m/z 453.1 (M+H)⁺,

Example 165-[1-(4-chlorophenyl)ethyl]-7-(5-hydroxy-2-methylphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting (5-hydroxy-2-methylphenyl)boronic acid formethyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® Rf apparatus using asilica gel cartridge (4 g) eluted with 40% ethyl acetate/cyclohexane.The residue was triturated with a little ethyl acetate/diisopropyl ether(1:1). The solid was collected by vacuum filtration and was driedovernight in a vacuum oven to give the titled compound. ¹H NMR (600 MHz,DMSO-¹H NMR (600 MHz, DMSO-d₆) δ ppm 9.59 (s, 1H), 7.44-7.34 (m, 4H),7.19-7.14 (m, 1H), 6.98 (d, J=2.6 Hz, 1H), 6.84 (dd, J=8.3, 2.6 Hz, 1H),6.35 (q, J=7.0 Hz, 1H), 2.60 (s, 3H), 2.11 (s, 3H), 1.73 (d, J=7.1 Hz,3H); MS (ESI+) m/z 396.1 (M+H)⁺.

Example 17N-(2-fluoro-5-{5-[2-fluoro-5-(trifluoromethyl)benzyl]-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamido-4-fluorophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and2-(bromomethyl)-1-fluoro-4-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 22%.

¹H NMR (400 MHz, CD₃OD): δ 8.21-8.19 (m, 1H), 8.00-7.99 (d, J=5.2 Hz,1H), 7.73-7.71 (m, 1H), 7.62 (br, 1H), 7.45-7.41 (t, J=9.2 Hz, 1H),7.24-7.20 (t, J=8.8 Hz, 1H), 5.09-5.05 (m, 2H), 2.66 (s, 3H), 1.95 (s,3H). m/z 479.2

Example 18N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methylphenyl)acetamide

The titled compound was obtained using the reaction conditions describedfor Example 6 substitutingN-(4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetamidefor methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® Rf apparatus using asilica gel cartridge (4 g) eluted with 60% ethyl acetate/cyclohexane. Asecond flash chromatography on a Teledyne Isco CombiFlash® Rf apparatususing a silica gel cartridge (4 g) eluted with 3%methanol/dichloromethane. The residue was triturated with a little ethylacetate/diisopropyl ether (1:1). The residue was dried overnight in avacuum oven to give the titled compound. ¹H NMR (500 MHz, DMSO-d₆) δ ppm10.07 (s, 1H), 7.84 (d, J=2.2 Hz, 1H), 7.62 (dd, J=8.4, 2.3 Hz, 1H),7.39 (s, 4H), 7.30 (d, J=8.5 Hz, 1H), 6.35 (q, J=7.0 Hz, 1H), 2.61 (s,2H), 2.39 (s, 1H), 2.16 (s, 3H), 2.04 (s, 3H), 1.99 (s, 1H), 1.73 (d,J=7.0 Hz, 3H), 1.30 (s, 2H); MS (ESI+) m/z 437.1 (M+H)⁺.

Example 197-(4-fluorophenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-oneStep 1: (Z)-ethyl 3-aminobut-2-enoate

Aqueous methane amine (250 ml, 922 mmol) was added dropwise to anaqueous NaOH solution (2M) (300 ml) to give methane amine gas. The gaswas bubbled through ethyl 3-oxobutanoate (60 g, 461 mmol). The mixturewas stirred at room temperature overnight. MTBE was added. The organiclayer was separated and washed with water to pH═8, dried over Na₂SO₄,concentrated under reduced pressure to get (Z)-ethyl 3-aminobut-2-enoate(45 g, 348 mmol, 76% yield).

Step 2: 2-chloro-1-(4-fluorophenyl)-2-oxoethyl acetate

To an ice cooled solution of Oxalyl chloride (49.5 ml, 566 mmol) and DMF(18.25 ml, 236 mmol) in DCM (1600 ml) was added2-acetoxy-2-(4-fluorophenyl)acetic acid (100 g, 471 mmol) in DCM (1600ml). The mixture was stirred at 0° C. for 1 hour. The solvent wasremoved under reduced pressure to get2-chloro-1-(4-fluorophenyl)-2-oxoethyl acetate (97 g, 421 mmol, 89%yield), which was directly used to the next step.

Step 3: (Z)-ethyl2-(2-acetoxy-2-(4-fluorophenyl)acetyl)-3-(methylamino)but-2-enoate

To a solution of (Z)-ethyl 3-(methylamino)but-2-enoate (50 g, 349 mmol)in THF (1200 ml) and pyridine (28.2 ml, 349 mmol)2-chloro-1-(4-fluorophenyl)-2-oxoethyl acetate (97 g, 419 mmol) in THF(1200 ml) was added at 0° C. The mixture was stirred at room temperatureovernight. Water and EtOAc were added. The mixture was extracted withEtOAc. The organic layer was concentrated and purified by pre-TLC to get(Z)-ethyl2-(2-acetoxy-2-(4-fluorophenyl)acetyl)-3-(methylamino)but-2-enoate (90g, 267 mmol, 76% yield),which was directly used to the next step.

Step 4: 5-(4-fluorobenzoyl)-3-methylisoxazole-4-carboxylate

To a solution of (Z)-ethyl2-(2-acetoxy-2-(4-fluorophenyl)acetyl)-3-(methylamino)but-2-enoate (90g, 267 mmol) in acetic acid (800 ml) hydroxylamine hydrochloride (22.25g, 320 mmol) was added. The mixture was refluxed for 30 min. The solventwas removed under reduced pressure. Then MTBE was added. The solutionwas washed with water, Na₂CO₃ and water, then dried and concentrated toget ethyl5-(acetoxy(4-fluorophenyl)methyl)-3-methylisoxazole-4-carboxylate (90 g,280 mmol, 105% yield) which was directly used to the next step.

Step 5: 5-(4-fluorobenzoyl)-3-methylisoxazole-4-carboxylate

To a solution of ethyl5-((4-fluorophenyl)(hydroxy)methyl)-3-methylisoxazole-4-carboxylate (40g, 143 mmol) in Jones' reagent (80 ml, 143 mmol) (26.73 g chromiumtrioxide and 23 mL concentrated H₂SO₄ was diluted to 100 ml with waterto get Jones' reagent.) The mixture was stirred at room temperature for4 hours. The precipitated salts were filtered off and washed withacetone and the acetone layer was stirred with Na₂SO₃ for 2 hours. Thesolution was filtered and the acetone was removed under reducedpressure. The solid residue was washed with ethanol and dried to getethyl 5-(4-fluorobenzoyl)-3-methylisoxazole-4-carboxylate (34.5 g, 124mmol, 87% yield).

Step 6: 7-(4-fluorophenyl)-3-methylisoxazolo[4,5-d]pyridazin-4(5H)-one(23 g, 94 mmol, 75% yield)

To a solution of ethyl5-(4-fluorobenzoyl)-3-methylisoxazole-4-carboxylate (34.5 g, 124 mmol)in ethanol (400 ml) hydrazine hydrate (12.44 g, 249 mmol) was added. Themixture was stirred at room temperature for 4 hours. The white solid wascollected and washed with ethanol give7-(4-fluorophenyl)-3-methylisoxazolo[4,5-d]pyridazin-4(5H)-one (23 g, 94mmol, 75% yield).

Step 7:7-(4-fluorophenyl)-3-methyl-5-(4-(trifluoromethyl)benzyl)isoxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (100mg, 0.408 mmol) in N,N-dimethylformamide (2 mL), NaH (14.68 mg, 0.612mmol) was added. The mixture was stirred at room temperature for 15minutes, and then 1-(bromomethyl)-4-(trifluoromethyl)benzene (117 mg,0.489 mmol) was added. The mixture was stirred at room temperatureovernight. 60% of the starting material was remaining. The mixture wasquenched with water. The solid precipitate was collected and washed withwater and methanol, then dried to give7-(4-fluorophenyl)-3-methyl-5-(4-(trifluoromethyl)benzyl)isoxazolo[4,5-d]pyridazin-4(5H)-one(36 mg, yield 21.9%) as a solid.

¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.09 (m, 2H), 7.62 (dd, J=8.4, 2.3 Hz,2H), 7.59 (m, 2H), 7.44 (m, 2H), 5.52 (s, 2H), 2.60 (s, 3H); MS (ESI+)m/z 404.0 (M+H)⁺.

Example 205-(2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

A 100 mg/mL slurry of NaH in N,N-dimethylformamide was prepared freshfrom solid NaH. In a 4 mL vial equipped with a stirrer was added3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (12.40 mg, 0.08 mmol)dissolved in 300 μL of N,N-dimethylformamide. At room temperaturewithout nitrogen, 27.03 μL (2.70 mg, 1.5 equivalents, 0.11 mmol) ofsodium hydride was added. Bubbles appeared, and the reaction was allowedto react for 30 minutes with stirring at room temperature. To thismixture, 130 !IL of a solution of 1-(bromomethyl)-2-fluorobenzene from a0.6 mmol pre-weighed vial (1 equivalent, 15.1 mg, 0.08 mmol) inN,N-dimethylformamide (1 mL), was added. The reaction was then stirredfor 6 hours at room temperature. The reaction was quenched with water(100 μL), and the reaction mixture was purified directly by preparativeliquid chromatography (Method C, 0.5-8.5 minutes linear gradient 45-75%A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.39-7.33 (m, 1H), 7.27-7.20 (m,2H), 7.20-7.13 (m, 1H), 5.36 (s, 2H), 2.57 (s, 3H), 2.49 (s, 3H); MS(APCI⁻) m/z 274.1(M+H)⁺.

Example 215-[1-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.163 mmol, Example 39-Step 5) in ethanol/toluene (1:1, 3 mL)was combined with sodium carbonate (25.9 mg, 0.244 mmol) and(2,5-dimethoxyphenyl)boronic acid (29.6 mg, 0.163 mmol). Thentetrakis(triphenylphosphine)palladium(0) (18.81 mg, 0.016 mmol) wasadded, and the mixture was heated in a CEM® microwave reactor for 30minutes at 130° C. under an argon atmosphere. The reaction mixture waspartitioned between water and ethyl acetate. The organic fraction wasthen washed with brine, dried over MgSO₄, and concentrated under reducedpressure. The residue was stirred with ethyl acetate, and theprecipitate was collected and dried in a vacuum oven overnight. Thematerial was purified by flash chromatography on a Teledyne IscoCombiFlash® Rf apparatus using a silica gel cartridge (4 g) eluted with20% ethyl acetate/cyclohexane. The residue was dried in a vacuum ovenovernight to give the titled compound. ¹H NMR (600 MHz, DMSO-d₆) δ ppm7.42 (s, 4H), 7.20-7.11 (m, 2H), 6.99-6.93 (m, 1H), 6.32 (q, J=7.0 Hz,1H), 3.77-3.66 (m, 7H), 3.64 (s, 1H), 2.59 (s, 3H), 1.73 (d, J=7.0 Hz,3H).

Example 225-[1-(4-chlorophenyl)ethyl]-7-(5-fluoropyridin-3-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 4 substituting (5-fluoropyridin-3-yl)boronic acid (23 mg, 0.16mmol) for (2,6-difluoropyridin-4-yl)boronic acid. Purification wasachieved by preparative liquid chromatography (Method C, 0.5-8.5 minuteslinear gradient 45-75% A). ¹H NMR (400 MHz,DMSO-d₆/D₂O, Temperature=90°C.) δ ppm 9.13-9.04 (m, 1H), 8.69 (d, J=2.6 Hz, 1H), 8.20-8.14 (m, 1H),7.49-7.42 (m, 2H), 7.40-7.35 (m, 2H), 6.33 (q, J=7.0 Hz, 1H), 2.62 (s,3H), 1.83 (d, J=7.0 Hz, 3H); MS (APCI⁺) m/z 385 (M+H)⁺.

Example 235-(4-chlorobenzyl)-7-(3-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (3-fluorophenyl)boronic acid (47.2 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 37%

1H NMR (CDCl3, 400 MHz):δ 7.97 (d, J=7.94 Hz, 1H), 7.86 (dd, J=11.69,1.98 Hz, 1H), 7.38-7.55 (m, 3H), 7.32 (d, J=8.38 Hz, 2H), 7.20 (td,J=8.27, 1.98 Hz, 1H), 5.44 (s, 2H), 2.71 (s, 3H); m/z 369.8.

Example 24N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)methanesulfonamide

The titled compound was prepared using the procedure described inExample 4 substituting (3-(methylsulfonamido)phenyl)boronic acid (34 mg,0.16 mmol) for (2,6-difluoropyridin-4-yl)boronic acid. Purification wasachieved by preparative liquid chromatography (Method C, 0.5-8.5 minuteslinear gradient 45-75% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O, Temperature=90°C.) δ ppm 8.02 (t, J=2.0 Hz, 1H), 7.82 (dt, J=7.9, 1.3 Hz, 1H), 7.55 (t,J=8.0 Hz, 1H), 7.47-7.43 (m, 2H), 7.40-7.35 (m, 3H), 6.35 (q, J=7.0 Hz,1H), 3.04 (s, 3H), 2.62 (s, 3H), 1.82 (d, J=7.0 Hz, 3H); MS (APCI+) m/z459 (M+H)⁺.

Example 255-[2-fluoro-5-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting2-(bromomethyl)-1-fluoro-4-(trifluoromethyl)benzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 60-100% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.81-7.75 (m,1H), 7.71 (dd, J=6.7, 2.4 Hz, 1H), 7.47 (t, J=9.2 Hz, 1H), 5.42 (s, 2H),2.57 (s, 3H), 2.49 (s, 3H); MS (APCI⁺) m/z 342.0 (M+H)⁺.

Example 267-(2-methoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2-methoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1. Yield 19%.

¹H NMR (400 MHz, CDCl₃): δ 8.77-8.75 (m, 2H), 7.94-7.93 (m, 2H),7.55-7.53 (m, 1H), 7.48-7.45 (m, 1H), 7.21-7.19 (m, 1H), 7.11-7.09 (m,1H), 5.73 (s, 2H), 3.84 (s, 3H), 2.64 (s, 3H). m/z 348.4.

Example 27N-{3-[5-(4-chlorobenzyl)-3-(methoxymethyl)-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamideStep 1: methyl 2-(methoxymethyl)-4-oxo-4,5-dihydrofuran-3-carboxylate

The reaction was run in duplicate and combined for purification. To asolution of methyl 4-methoxy-3-oxobutanoate (10 g, 68.4 mmol) in toluene(150 mL) was added magnesium ethoxide (12.67 g, 89 mmol) at roomtemperature. The mixture was stirred at 110° C. for 4 hours. Thereaction was cooled to 0° C. and solid was removed from the solution.2-Chloroacetyl chloride (14.00 ml, 137 mmol) was added dropwise, and themixture was stirred at room temperature overnight. The duplicatereaction mixtures were combined. The mixture was diluted by the additionof water and extracted with ethyl acetate (200 mL×3). The organic phasewas dried over Na₂SO₄ and concentrated under reduced pressure. Theresidue was purified by column chromatography on silica gel and elutedwith EtOAc/PE to give the titled compound (10 g, yield 39%). ¹H NMR (400MHz, CDCl₃) δ ppm 4.59 (s, 2H), 4.52 (s, 2H), 3.84-3.81 (m, 3H), 3.45(s, 3H).

Step 2: methyl5-(hydroxymethyl)-3-(methoxymethyl)-1,2-oxazole-4-carboxylate

To a solution of methyl2-(methoxymethyl)-4-oxo-4,5-dihydrofuran-3-carboxylate (9 g, 48.3 mmol,Step 1) in anhydrous ethanol (5 mL) was added sodium acetate (5.95 g,72.5 mmol) and NH₂OH.HCl (4.03 g, 58.0 mmol). The mixture was heated toreflux for 1 hour. The solvent was removed under reduced pressure. Theresidue was diluted with water and extracted with ethyl acetate (200mL×3). The organic phase was washed with brine, dried over Na₂SO₄, andconcentrated under reduced pressure to give a residue that was purifiedby column chromatography on silica gel (EtOAc/PE, 1:20˜5) to give thetitled compound (2.3 g, yield 23%). ¹H NMR (400 MHz, CDCl₃) δ ppm 4.92(s, 2H), 4.69 (s, 2H), 3.91 (s, 3H), 3.44 (s, 3H).

Step 3: methyl 5-formyl-3-(methoxymethyl)-1,2-oxazole-4-carboxylate

The reaction was run in triplicate and combined for purification. To asolution of methyl5-(hydroxymethyl)-3-(methoxymethyl)-1,2-oxazole-4-carboxylate (0.5 g,2.48 mmol, Step 2) in anhydrous dichloromethane (10 mL) was addedDess-Martin periodinane (2.108 g, 4.97 mmol). The mixture was stirred atroom temperature for overnight. All three reaction mixtures werecombined. The mixture was diluted by the addition of water and extractedwith dichloromethane (50 mL×3). The organic phase was dried over Na₂SO₄,filtered and concentrated under reduced pressure to give a residue thatwas purified by column chromatography on silica gel (EtOAc/PE, 1:20˜5)to give the titled compound (0.78 g, yield 55%). ¹H NMR (400 MHz, CDCl₃)δ ppm 10.34 (s, 1H), 4.79 (s, 2H), 4.00 (s, 3H), 3.48 (s, 3H).

Step 4: 3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of methyl5-formyl-3-(methoxymethyl)-1,2-oxazole-4-carboxylate (1.03 g, 5.17 mmol,Step 3) in anhydrous ethanol (20 mL) was added hydrazine (0.812 mL, 25.9mmol). The mixture was stirred at room temperature for overnight. Thesolvent was removed under reduced pressure to give a residue that wasdiluted with water and extracted with dichloromethane (50 mL×3). Theorganic phase was dried over Na₂SO₄ and concentrated under reducedpressure to give the titled compound (1 g, yield 96%). ¹H NMR (400 MHz,CDCl₃) δ ppm 8.36 (s, 1H), 4.93 (s, 1H), 3.55 (s, 1H).

Step 5: 7-bromo-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(1 g, 5.52 mmol, Step 4) in CH₃OH (20 mL) was added LiOH (0.66 g, 27.6mmol) and Br₂ (0.853 mL, 16.56 mmol) at 0° C. The mixture was stirred atthe reflux temperature for overnight. After cooling to room temperature,the solvent was removed under reduced pressure to give a residue thatwas diluted by the addition of water and extracted with ethyl acetate(50 mL×3). The organic phase was dried over Na₂SO₄ and concentratedunder reduced pressure to give the titled compound (0.85 g, yield 59%).¹H NMR (400 MHz, methanol-d₄) δ ppm 4.86 (s, 2H), 3.49 (s, 3H).

Step 6:7-bromo-5-(4-chlorobenzyl)-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (0.27 g,1.05 mmol, Step 5) in N,N-dimethylformamide (10 mL) was added K₂CO₃(0.29 g, 2.11 mmol) and 1-chloro-4-(chloromethyl) benzene (0.25 g, 1.58mmol) at 0° C. The mixture was stirred at 50° C. for 4 hours. Themixture was diluted with water and extracted with ethyl acetate (50mL×3). The combined organic phase was washed with brine and concentratedunder reduced pressure. The residue was purified by columnchromatography on silica gel to give the titled compound (0.36 g, yield89%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.44-7.38 (m, 2H), 7.35-7.30 (m,3H), 5.33 (s, 2H), 4.89 (s, 2H), 3.53 (s, 3H).

Step 7:N-{3-[5-(4-chlorobenzyl)-3-(methoxymethyl)-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.18 g, 0.46 mmol, Step 6) in 1,4-dioxane (15 mL) and water (5 mL) wasadded (3-acetamidophenyl)boronic acid (0.084 g, 0.468 mmol), K₂CO₃ (0.16g, 1.17 mmol) and tetrakis(triphenylphosphine)palladium(0) (0.054 g,0.047 mmol). After stirring at 80° C. overnight, the mixture was dilutedwith water and extracted with ethyl acetate (50 mL×3). The organic phasewas washed with brine and concentrated under reduced pressure to supplya residue that was purified by preparative HPLC (method B) to give thetitled compound (0.079 g, yield 38%). ¹H NMR (400 MHz, CDCl₃) δ ppm 8.21(s, 1H), 7.91 (d, J=7.5 Hz, 1H), 7.78 (d, J=7.5 Hz, 1H), 7.56-7.43 (m,3H), 7.33 (d, J=8.4 Hz, 2H), 5.45 (s, 2H), 4.97 (s, 2H), 3.56 (s, 3H),2.26 (s, 3H).

Example 285-[4-chloro-3-(trifluoromethyl)benzyl]-7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 19, 100 mg, 0.408 mmol) in N,N-dimethylformamide (2 mL) wasadded NaH (14.68 mg, 0.612 mmol). The mixture was stirred at roomtemperature for 15 minutes, and then4-(bromomethyl)-1-chloro-2-(trifluoromethyl)benzene (134 mg, 0.489 mmol)was added. The solid was collected by filtration and washed with waterand methanol to give the titled compound. ¹H NMR (400 MHz, DMSO-d₆) δppm 8.09-8.06 (m, 2H), 7.93 (s, 1H), 7.68-7.65 (m, 2H), 7.42-7.33 (m,2H), 5.51 (s, 2H), 2.59 (s, 3H); MS (APCI⁺) m/z 438.0 (M+H)⁺.

Example 29N-(2-fluoro-5-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamido-4-fluorophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and1-(bromomethyl)-4-(trifluoromethyl)benzene for 4-(bromomethyl)pyridinein Step 2. Yield 14%.

¹H NMR (400 MHz, CD₃OD): δ 8.02 (s, 1H), 8.01-7.99 (d, J=6.8 Hz, 1H),7.59-7.57 (t, J=8.0 Hz, 2H), 7.46-7.41 (m, 3H), 5.15-5.11 (m, 1H),4.94-4.91 (m, 1H), 2.66 (s, 3H), 1.98 (s, 3H). m/z 461.2.

Example 305-(4-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 1-(bromomethyl)-4-fluorobenzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 45-75% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.39-7.34 (m,2H), 7.20-7.13 (m, 2H), 5.29 (s, 2H), 2.57 (s, 3H), 2.50 (s, 3H); MS(APCI⁺) m/z 274.1 (M+H)⁺.

Example 315-[(1S)-1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The individual enantiomers of the mixture of Example 114 were separatedby preparative chiral chromatography (WHELK-O® 1 (S,S), 30×250 mmcolumn, 5 μm, concentration of 75 mg/mL in CH₃OH/CH₂Cl₂ (8:2), flow rate75 mL/minute; 20% CH₃OH in CO₂ at 100 psi=6.89 bar) to afford the titlecompound as the first-eluting enantiomer with a retention time of 4.6minutes. Stereocenter arbitrarily assigned. ¹H NMR (300 MHz, CDCl₃) δppm 7.41-7.35 (m, 2H), 7.31-7.26 (m, 2H), 6.33 (q, J=7.1, 7.1, 7.1 Hz,1H), 2.66 (s, 3H), 2.56 (s, 3H), 1.77 (d, J=7.1 Hz, 3H); MS (DCI/NH₃)m/z 304 (M+H)⁺, 321 (M+NH₄)⁺.

Example 327-(2,4-dimethoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 19%.

¹H NMR (400 MHz, CD³OD): δ 7.70-7.66 (m, 2H), 7.37-7.35 (d, J=8.4 Hz,1H), 7.16-7.14 (d, J=8.8 Hz, 1H), 6.71-6.66 (m, 2H), 5.41 (s, 2H), 3.93(s, 6H), 3.81 (s, 3H), 2.63 (s, 3H). m/z 475.4.

Example 33N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-2-methoxyphenyl)acetamideStep 1:N-(2-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetamide

A mixture of2-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (13 g,52.2 mmol) and acetic anhydride (50 mL, 530 mmol) in acetic acid(10 mL)was stirred at room temperature for 16 hours. The mixture wasconcentrated, and the residue was triturated with diethyl ether. Thesolid was collected by filtration, washed with diethyl ether, and driedto give the titled compound. ¹H NMR (300 MHz, DMSO-d₆) δ ppm 9.23 (s,1H), 8.10 (d, J=7.8 Hz, 1H), 7.28 (d, J=6.6 Hz, 1H), 7.04 (t, J=7.5 Hz,1H), 3.73 (s, 3H), 2.12 (s, 3H), 1.30 (s, 12H); MS (ESI+) m/z 292(M+H)⁺.

Step 2: Under argon,7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(70 mg, 0.190 mmol, Example 39-Step 5) was suspended in toluene andethanol (4 mL, 1:1). 2 M Aqueous sodium bicarbonate (0.142 mL, 0.285mmol) andN-(2-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetamide(55.3 mg, 0.190 mmol, Step 1) were added followed bytetrakis(triphenylphosphine)palladium(0) (21.94 mg, 0.019 mmol). Thereaction mixture was heated with stirring in a Biotage® microwavereactor at 130° C. for 30 minutes. The reaction mixture was thenpartitioned between water and ethyl acetate. The organic fraction waswashed with brine, dried over MgSO₄ and then concentrated under reducedpressure. The residue was purified by flash chromatography on a TeledyneIsco CombiFlash® Rf apparatus using a silica gel cartridge (4 g) elutedwith 3-5% methanol/dichloromethane. A second flash chromatography on aTeledyne Isco CombiFlash® Rf apparatus using a silica gel cartridge (4g) eluted with 3-5% methanol/dichloromethane was performed. The residuewas stirred overnight with diisopropyl ether, and the resultantprecipitate was collected and dried in a vacuum oven overnight to givethe titled compound. ¹H NMR (500 MHz, DMSO-d₆) δ ppm 9.60 (s, 1H),8.13-8.07 (m, 1H), 7.40 (s, 4H), 7.29-7.24 (m, 2H), 6.35 (q, J=7.0 Hz,1H), 3.42 (s, 3H), 2.60 (s, 3H), 2.14 (s, 3H), 1.75 (d, J=7.0 Hz, 3H).

Example 34N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

Example 78 (500 mg, 1.064 mmol) was separated by chiral super criticalfluid chromatography (method A) to give recovered racemic material (50.6mg, yield 11.2%), the enantiomer of the titled compound (162.9 mg, yield36.2%, Example 72) and the titled compound (208 mg, yield 46.2%). ¹H NMR(400 MHz, methanol-d₄) δ ppm 68.39 (s, 1H), 7.77 (d, J=0.0 Hz, 1H), 7.60(d, J=7.6 Hz, 1H), 7.41-7.36 (m, 3H), 7.25 (d, J=8.4 Hz, 2H), 6.32 (q,J=6.8 Hz, 1H), 2.55 (s, 3H), 2.09 (s, 3H), 1.80 (d, J=7.2 Hz, 3H); LCMS(method C) (ESI+) m/z 423 (M+H)⁺, retention time 3.366 minutes.

Example 35N-[4-methyl-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamideStep 1:(R)-7-bromo-3-methyl-5-(1-(4-(trifluoromethyl)phenyl)ethyl)isoxazolo[4,5-d]pyridazin-4(5H)-one

Into a 50-ml 3-neck bottom flask, was placed(S)-1-(4-(trifluoromethyl)phenyl)ethanol (455 mg, 2.391 mmol),7-bromo-3-methylisoxazolo[4,5-d]pyridazin-4(5H)-one (500 mg, 2.174mmol), and triphenylphosphine (684 mg, 2.61 mmol) in tetrahydrofuran (15ml). The solution was cooled to 0° C. (E)-diisopropyldiazene-1,2-dicarboxylate (0.507 ml, 2.61 mmol) was added dropwise tothe reaction mixture. The mixture was stirred for 3 h at roomtemperature. The solution was concentrated under vacuum and purified byHPLC-TLC, to give(R)-7-bromo-3-methyl-5-(1-(4-(trifluoromethyl)phenyl)ethyl)-isoxazolo[4,5-d]pyridazin-4(5H)-one(800 mg, 1.989 mmol, 92% yield).

Step 2:7-(5-amino-2-methylphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 35, 100 mg, 0.249 mmol),4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (63.8mg, 0.274 mmol), sodium carbonate (79 mg, 0.746 mmol), and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (18.19 mg,0.025 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (3 mL) and water(0.3 mL) in a 5 mL sealed tube. The reaction mixture was irradiated at100° C. for 60 minutes in a microwave reactor. The reaction mixture wasthen concentrated, and the residue was purified by silica gel columnchromatography eluted with EtOAc/PE (1:3) to give7-(5-amino-2-methylphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one.

Step 3:N-[4-methyl-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide

7-(5-Amino-2-methylphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(100 mg, 0.233 mmol) and triethylamine (23.62 mg, 0.233 mmol) werecombined in dichloromethane (10 mL). Acetyl chloride (18.32 mg, 0.233mmol) was added dropwise, and the reaction mixture was stirred atambient temperature for 1 hour. The reaction mixture was concentratedunder reduced pressure, and the residue was purified by silica gelcolumn chromatography eluted with EtOAc/PE (4:1) to give the titlecompound (11 mg, 8.1% yield). ¹H NMR (400 MHz, CD₃OD) δ ppm 1.88 (d,3H), 2.15 (s, 3H), 2.22 (s, 3H), 2.68 (s, 3H), 6.52 (q, 1H), 7.33 (d,1H), 7.65 (m, 5H), 7.82 (s, 1H); MS (ESI+) m/z 471.2 (M+H)⁺.

Example 365-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(221 mg, 0.60 mmol, Example 129-Step 6) in 1,4-dioxane (5 mL) and water(2 mL) was added (2,5-dimethoxyphenyl)boronic acid (109 mg, 0.6 mmol),K₂CO₃ (63.6 mg, 0.6 mmol) and tetrakis(triphenylphosphine)palladium(0)(69.3 mg, 0.6 mmol) at room temperature under nitrogen. After stirringat 80° C. overnight, the mixture was diluted with water and extractedwith ethyl acetate (20 mL×3). The organic phase was washed with brineand concentrated in vacuum. The residue was purified by preparative HPLC(method B) to give the titled compound (54.4 mg, yield 21%). ¹H NMR (400MHz, CDCl₃) δ ppm 7.40-7.36 (m, 2H), 7.25-7.21 (m, 2H), 6.99-6.95 (m,1H), 6.93 (s, 1H), 6.92-6.90 (m, 1H), 5.34 (s, 2H), 3.74 (d, J=3.1 Hz,6H), 3.02 (q, J=7.5 Hz, 2H), 1.36 (t, J=7.5 Hz, 3H); LCMS (method B)(ESI+) m/z 425.9 (M+H)⁺, retention time 3.324 minutes.

Example 377-(2,4-dimethoxyphenyl)-5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting4-(bromomethyl)-1-fluoro-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 21%.

¹H NMR (400 MHz, CD₃OD): δ 7.85-7.69 (m, 2H), 7.41-7.22 (m, 2H),6.74-6.62 (m, 2H), 5.47 (s, 2H), 3.88 (s, 3H), 3.81 (s, 3H), 2.63 (s,3H). m/z 463.4.

Example 383-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N,N-dimethylbenzamide

Sodium hydride (10.94 mg, 0.456 mmol, 18.23 mg of 60% dispersion in oil)was added to a solution of3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzamide(50 mg, 0.114 mmol, Example 59) dissolved in N,N-dimethylformamide (1mL). After 30 minutes, iodomethane (0.021 mL, 48.5 mg, 0.342 mmol) wasadded, and the reaction mixture was stirred for 3 hours. The reactionmixture was then partitioned between ethyl acetate and water. Theaqueous phase was extracted twice with ethyl acetate. The combinedorganic fractions were washed with brine, dried over MgSO₄ andconcentrated. The residue was purified by flash chromatography on aTeledyne Isco CombiFlash® apparatus using a RediSep® silica gelcartridge (4 g) eluted with 0-10% methanol/dichloromethane. The residuewas dried in a vacuum oven to give the titled compound (25 mg, yield47%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm 7.66 (dd, J=8.6, 2.2 Hz, 2H), 7.50(d, J=2.2 Hz, 2H), 7.44-7.36 (m, 9H), 7.29 (d, J=8.6 Hz, 2H), 6.31 (q,J=7.0 Hz, 2H), 4.00-3.93 (m, 0H), 3.84 (s, 7H), 3.33 (s, 1H), 2.99 (s,14H), 2.95 (s, 1H), 2.59 (s, 7H), 1.73 (d, J=7.0 Hz, 7H), 1.28 (s, 1H),1.26 (s, 3H), 1.23 (s, 1H), 1.09 (d, J=6.2 Hz, 3H).

Example 39N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamideStep 1: 3-bromo-4-methoxyaniline

To a solution of 2-bromo-1-methoxy-4-nitrobenzene (5.0 g, 21.55 mmol) inethanol (40 mL) and H₂O (20 mL) was added Zn (7.04 g, 108 mmol) andNH₄Cl (5.76 g, 108 mmol). The resulting mixture was stirred at 80° C.for 3 hours. Then the hot reaction mixture was filtered, and thefiltrate was concentrated. The aqueous phase was extracted withdichloromethane (100 mL×3). The organic layer was dried over Na₂SO₄,filtered and concentrated to give the titled compound which was usedwithout further purification.

Step 2: N-(3-bromo-4-methoxyphenyl)acetamide

To a solution of 3-bromo-4-methoxyaniline (3.03 g, 15.00 mmol, Step 1)in dichloromethane (50 mL) was added triethylamine (3.14 mL, 22.49 mmol)and acetic anhydride (1.698 mL, 18.00 mmol). The resulting mixture wasstirred at 25° C. for 3 hours. The mixture was poured into H₂O andextracted with dichloromethane (100 mL×3). The organic layer was driedover Na₂SO₄, filtered and concentrated. The residue was purified bycolumn chromatography on silica gel and eluted with EtOAc/PE to give thetitled compound (3.3 g, yield 90%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.67(d, J=2.2 Hz, 1H), 7.42 (dd, J=2.2, 8.8 Hz, 2H), 6.83 (d, J=8.8 Hz, 1H),3.89-3.82 (m, 3H), 2.20-2.10 (m, 3H).

Step 3:N-[4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]acetamide

To a solution of N-(3-bromo-4-methoxyphenyl)acetamide (2 g, 8.19 mmol)in dioxane (40 mL) was added4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-bi(1,3,2-dioxaborolane) (2.08 g,8.19 mmol), potassium acetate (0.77 mL, 8.19 mmol), and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (6.00 g,8.19 mmol, PdCl₂(dppf)). The mixture was refluxed for 3 hours under N₂.After cooling down to room temperature, the mixture was concentrated.The residue was purified by column chromatography on silica gel andeluted with EtOAc/PE to give the titled compound (1.3 g, yield 54%). ¹HNMR (400 MHz, CDCl₃) δ ppm 7.79 (dd, J=2.6, 8.8 Hz, 1H), 7.48 (d, J=2.6Hz, 1H), 7.32 (br. s., 1H), 6.83 (s, 1H), 3.79 (s, 3H), 2.11 (s, 3H),1.33 (s, 12H).

Step 4: 1-(1-bromoethyl)-4-chlorobenzene

A solution of 1-(4-chlorophenyl)ethanol (3.5 g, 22.35 mmol) in drytetrahydrofuran (150 mL) was treated dropwise with PBr₃ (0.927 mL, 9.83mmol). The mixture was heated at reflux for 1 hour, then cooled, andwashed twice with water. The organic fraction was dried andconcentrated. The residue was purified by column chromatography onsilica gel eluted with petroleumether to give the titled compound (6 g,purity 55%, yield 67.3%). LCMS (method A) (ESI+) m/z 221(M+H)⁺,retention time 1.405 minutes; ¹H NMR (400 MHz, CDCl₃) δ ppm 7.40-7.35(m, 2H), 7.34-7.29 (m, 2H), 5.17 (q, J=6.9 Hz, 1H), 2.03 (d, J=6.6 Hz,3H).

Step 5:7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 7-bromo-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(3 g, 13.04 mmol, Example 2-Step 5) in N,N-dimethylformamide (60 mL) wasadded potassium carbonate (3.61 g, 26.1 mmol), and then1-(1-bromoethyl)-4-chlorobenzene (6 g, purity 55%, 15.03 mmol, Step 1)was added in one portion. The mixture was stirred at room temperaturefor 4 hours. The reaction mixture was diluted with water and extractedwith ethyl acetate. The organic phase was washed with brine andconcentrated under reduced pressure. The residue was washed withmethanol, and the solid cake was air dried to give the titled compound(2.2 g, purity 90%, yield 41.2%). ¹H NMR (400 MHz CDCl₃) δ ppm 7.31 (d,J=8.4 Hz, 2H), 7.24 (d, J=8.8 Hz, 2H), 6.25-6.19 (m, 1H), 2.58 (s, 3H),1.72 (d, J=7.2 Hz, 3H).

Step 6:N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]-oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide

To a stirred solution of7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(1 g, 2.7 mmol, Step 5) in 1,2-dimethoxyethane (10 mL) and H₂O (2.5 mL)was addedN-[4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]acetamide(0.66 g, 2.27 mmol, Step 3), K₂CO₃ (1.12 g, 8.14 mmol) andtetrakis(tripehenylphosphine)palladium(0) (0.26 g, 0.228 mmol). Then themixture was stirred at 80° C. under nitrogen overnight. The mixture wasconcentrated to give a residue that was diluted with water and extractedwith ethyl acetate. The organic layers were dried and concentrated underreduced pressure. The residue was purified by preparatory HPLC (methodB) to give the titled compound (0.5 g, yield 40%). ¹H NMR (400 MHz,CDCl₃) δ ppm 7.63 (dd, J=2.4, 9.0 Hz, 1H), 7.56 (d, J=2.2 Hz, 1H), 7.45(d, J=8.4 Hz, 2H), 7.32-7.22 (m, 3H), 7.01 (d, J=8.8 Hz, 1H), 6.39 (q,J=7.1 Hz, 1H), 3.83 (s, 3H), 3.49 (s, 1H), 2.67 (s, 3H), 2.20 (s, 3H),1.82 (d, J=7.1 Hz, 3H); LCMS (method C) (ESI+) m/z 453.2 (M+H)⁺,retention time 3.251 minutes.

Example 40N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide

The enantiomers ofN-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide(0.4 g, 0.883 mmol, Example 39) were separated by chiral super criticalchromatograph (method B) to giveN-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide(0.09 g, yield 23%, Example 117) and the titled compound (0.08 g, yield20%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.56 (dd, J=2.6, 8.8 Hz, 1H), 7.48(d, J=2.6 Hz, 1H), 7.38 (d, J=8.4 Hz, 2H), 7.23 (d, J=8.8 Hz, 2H), 7.07(br. s., 1H), 6.95 (d, J=8.8 Hz, 1H), 6.32 (q, J=6.8 Hz, 1H), 3.76 (s,3H), 2.61 (s, 3H), 2.13 (s, 3H), 1.75 (d, J=7.1 Hz, 3H); LCMS (method C)(ESI+) m/z 453.2 (M+H)⁺, retention time 3.241 minutes.

Example 41N-(3-{5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamidophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-fluoro-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 21%.

¹H NMR (400 MHz, CD₃OD): δ 7.85-7.69 (m, 2H), 7.41-7.22 (m, 2H),6.74-6.62 (m, 2H), 5.47 (s, 2H), 3.88 (s, 3H), 3.81 (s, 3H), 2.63 (s,3H). m/z 463.4.

Example 425-(4-chlorobenzyl)-7-(3,4-difluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (3,4-difluorophenyl)boronic acid (53.4 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 53%.

¹H NMR (CDCl₃, 400 MHz):δ 7.94-8.08 (m, 2H), 7.46 (d, J=8.38 Hz, 2H),7.31-7.40 (m, 3H), 5.45 (s, 2H), 2.74 (s, 3H). m/z 387.8.

Example 435-[4-fluoro-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting4-(bromomethyl)-1-fluoro-2-(trifluoromethyl)benzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 60-100% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.76 (dd,J=7.1, 2.2 Hz, 1H), 7.66 (ddd, J=7.8, 4.9, 2.3 Hz, 1H), 7.47 (dd,J=10.7, 8.6 Hz, 1H), 5.37 (s, 2H), 2.57 (s, 3H), 2.51 (s, 3H); MS(APCI⁺) m/z 342.1 (M+H)⁺.

Example 443,7-dimethyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 4-(bromomethyl)pyridine for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 10-40% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 8.75-8.71 (m,2H), 7.74-7.70 (m, 2H), 5.55 (s, 2H), 2.57 (s, 3H), 2.52 (s, 3H); MS(APCI⁺) m/z 257.1 (M+H)⁺.

Example 45N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-4-methoxyphenyl}acetamideStep 1: 3-bromo-4-methoxyaniline

To a solution of 2-bromo-1-methoxy-4-nitrobenzene (5 g, 21.55 mmol) inethanol (40 mL) and H₂O (20 mL) was added zinc (7.04 g, 108 mmol) andNH₄Cl (5.76 g, 108 mmol). The resulting mixture was stirred at 80° C.for 3 hours. Then the hot reaction mixture was filtered, and thefiltrate was concentrated. The aqueous phase was extracted with ethylacetate. The organic layer was dried over Na₂SO₄ and concentrated togive the titled compound (3.3 g, yield 76%) that was used for the nextstep without further purification. ¹H NMR (400 MHz, methanol-d₄) δ ppm7.01 (s, 1H), 6.88-6.86 (d, J=8.0 Hz, 1H), 6.75-6.72 (d, J=12.0 Hz, 1H),3.81 (s, 3H).

Step 2: N-(3-bromo-4-methoxyphenyl)acetamide

To a solution of 3-bromo-4-methoxyaniline (3.1 g, 15.3 mmol, Step 1) indichloromethane (30 mL) was added acetic anhydride (1.74 mL, 18.4 mmol)and triethylamine (3.2 mL, 23.0 mmol). The resulting mixture was stirredat room temperature for 3 hours. The solvent was removed to give thetitled compound (3.6 g, yield 96%) that was used for the next stepwithout further purification. ¹H NMR (400 MHz, methanol-d₄) δ ppm7.81-7.80 (s, 1H), 7.43-7.40 (d, J=12.0 Hz, 1H), 6.97-6.95 (d, J=8.0 Hz,1H), 3.83 (s, 3H), 2.08 (s, 3H).

Step 3:N-[4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]acetamide

To a solution of N-(3-bromo-4-methoxyphenyl)acetamide (2 g, 8.19 mmol,Step 2) in 1,4-dioxane (40 mL) was added4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-bi-1,3,2-dioxaborolane (3.12 g,12.29 mmol), potassium acetate (2.41 g, 24.58 mmol) and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.60 g,0.82 mmol, Pd(dppf)Cl₂). The resulting mixture was stirred at 110° C.for 3 hours under N₂. After cooling down to room temperature, themixture was concentrated to give a residue that was purified by columnchromatography on silica gel and eluted with EtOAc/PE to give the titledcompound (800 mg, yield 33%). ¹H NMR (400 MHz, methanol-d₄) δ ppm7.67-7.63 (d, J=16.0 Hz, 1H), 7.42-7.40 (d, J=8.0 Hz, 1H), 6.92-6.84 (m,1H), 3.78 (s, 3H), 2.08 (s, 3H), 1.33 (s, 3H).

Step 4:N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-4-methoxyphenyl}acetamide

To a solution ofN-[4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]acetamide(750 mg, 2.58 mmol, Step 3) in 1,2-dimethoxyethane (10 mL) and H₂O (2.5mL) was added7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(1.09 g, 3.09 mmol, Example 2-Step 6), K₂CO₃ (1.07 g, 7.73 mmol) andtetrakis(triphenylphosphine)palladium(0) (298 mg, 0.258 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the mixture was concentrated to give aresidue that was washed with methanol and dried to obtain the titledcompound (281 mg, yield 24%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.97 (s,1H), 7.71-7.66 (m, 2H), 7.41-7.38 (m, 4H), 7.17-7.15 (d, J=8.0 Hz, 1H),5.36 (s, 2H), 3.73 (s, 3H), 2.57 (s, 3H), 2.00 (s, 3H); LCMS (method D)(ESI+) m/z 439 (M+H)⁺, retention time 2.46 minutes.

Example 465-[2-fluoro-5-(trifluoromethyl)benzyl]-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2-methoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and2-(bromomethyl)-1-fluoro-4-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 15%

¹H NMR (400 MHz, CD₃OD): δ 7.76-7.73 (m, 2H), 7.53-7.51 (m, 1H),7.40-7.34 (m, 1H), 7.19-7.17 (m, 1H), 7.10-7.08 (m, 1H), 5.58 (s, 2H),3.82 (s, 3H), 2.64 (s, 3H). m/z 433.4.

Example 475-(4-chlorobenzyl)-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(280 mg, 0.73 mmol, Example 51-Step 6) in N,N-dimethylformamide (2 mL)and water (0.5 mL) was added (2,5-dimethoxyphenyl)boronic acid (161 mg,0.88 mmol), K₂CO₃ (254 mg, 1.83 mmol) andtetrakis(triphenylphosphine)palladium(0) (85 mg, 0.074 mmol). Afterstirring at 80° C. overnight under nitrogen, the mixture was dilutedwith water and extracted with ethyl acetate. The organic phase waswashed with brine and then concentrated under reduced pressure to give aresidue that was purified by preparative HPLC (method C) to give thetitled compound (33 mg, yield 10%). ¹H NMR (400 MHz, CDCl₃) δ ppm7.43-7.36 (m, 1H), 7.17-7.09 (m, 1H), 6.97 (d, J=2.2 Hz, 1H), 5.38 (s,2H), 3.72 (d, J=11.0 Hz, 6H), 2.46-2.38 (m, 1H), 1.20-1.13 (m, 4H); LCMS(method B) (ESI+) m/z 438.1 (M+H)⁺, retention time 3.365 minutes.

Example 487-(2,4-dimethoxyphenyl)-5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting2-(bromomethyl)-1-fluoro-4-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 16%

1H NMR (400 MHz, CD₃OD): δ 7.77-7.64 (m, 2H), 7.38-7.28 (m, 2H),6.72-6.61 (m, 2H), 5.56 (s, 2H), 3.87 (s, 3H), 3.82-3.77 (m, 3H), 2.63(s, 3H). m/z 463.4.

Example 49N-[3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-(trifluoromethoxy)phenyl]acetamideStep 1:N-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4-(trifluoromethoxy)phenyl)acetamide

3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-4-(trifluoromethoxy)aniline(19.0 g, 62.7 mmol), triethylamine (19.03 g, 188 mmol), anddichloromethane (200 mL) were combined under an atmosphere of nitrogen.Then the mixture was cooled to 0° C. and acetyl chloride (5.91 g, 75mmol) was added dropwise. The resultant mixture was allowed to warm toambient temperature with continued stirring overnight. The reactionmixture was concentrated under reduced pressure, and the residue waspurified by column chromatography on silica gel eluted with 25% ethylacetate/hexane to give a mixture of the titled compound and(5-acetamido-2-(trifluoromethoxy)phenyl)boronic acid.

Step 2:N-[3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-(trifluoromethoxy)phenyl]acetamide

Under argon,7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(70 mg, 0.190 mmol, Example 39-Step 5) was suspended in toluene andethanol (4 mL, 1:1). 2 M Aqueous sodium bicarbonate (0.142 mL, 0.285mmol) andN-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4-(trifluoromethoxy)phenyl)acetamide(65.5 mg, 0.190 mmol, Step 1) were added followed bytetrakis(triphenylphosphine)palladium(0) (21.94 mg, 0.019 mmol). Thereaction mixture was heated with stirring in a Biotage® microwavereactor at 130° C. for 30 minutes. The reaction mixture was thenpartitioned between water and ethyl acetate. The organic fraction waswashed with brine, dried over MgSO₄ and then concentrated under reducedpressure. The residue was purified by flash chromatography on a TeledyneIsco CombiFlash® Rf apparatus using a silica gel cartridge (4 g) elutedwith 3-5% methanol/dichloromethane. The residue was dried in a vacuumoven overnight to give the titled compound (37 mg, yield 38%). ¹H NMR(600 MHz, DMSO-d₆) δ ppm 10.39 (s, 1H), 8.06 (d, J=2.6 Hz, 1H), 7.87(dd, J=9.1, 2.7 Hz, 1H), 7.57 (dd, J=9.1, 1.5 Hz, 1H), 7.43-7.35 (m,3H), 6.33 (q, J=7.0 Hz, 1H), 2.60 (s, 2H), 2.09 (s, 3H), 1.73 (d, J=7.0Hz, 3H), 1.29 (s, 1H), 1.08-1.01 (m, 1H).

Example 505-[4-methoxy-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 50-80% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.64-7.56 (m,2H), 7.23 (d, J=8.6 Hz, 1H), 5.29 (s, 2H), 3.86 (s, 3H), 2.57 (s, 3H),2.50 (s, 3H); MS (APCI⁻) m/z 354.0 (M+H)⁺.

Example 51N-{3-[5-(4-chlorobenzyl)-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamideStep 1: methyl 2-cyclopropyl-4-oxo-4,5-dihydrofuran-3-carboxylate

To a solution of magnesiumethanolate (19.32 g, 169 mmol) in toluene (80mL) was slowly added methyl 3-cyclopropyl-3-oxopropanoatel (20 g, 141mmol) at 0° C. After stirring for 1 hour, acetonitrile (80 mL) was addedfollowed by the addition of 2-chloroacetyl chloride (15.89 g, 141 mmol)at 0° C. The mixture was allowed to warm to room temperature and left tostir for 2 hours. A diluted solution of sulfuric acid (1 mL acid in 30mL ice/water) was added, followed by extraction with tert-butylmethylether. The combined organic fractions were dried over Na₂SO₄ andfiltered. To the filtrate was added a solution of triethylamine (49 mL,338 mmol) in tert-butylmethyl ether (150 mL). The reaction mixture wasstirred at room temperature overnight. The mixture was diluted withwater (200 mL), and extracted with dichloromethane. The organic phasewas concentrated under reduced pressure to supply a residue that waspurified by chromatography on silica gel and eluted with EtOAc/PE togive the titled compound (24 g, yield 94%). ¹H NMR (400 MHz, CDCl₃) δppm 4.50 (s, 1H), 4.33 (q, J=7.2 Hz, 2H), 3.18-3.08 (m, 1H), 1.40-1.32(m, 5H), 1.29-1.22 (m, 2H).

Step 2: methyl 3-cyclopropyl-5-(hydroxymethyl)-1,2-oxazole-4-carboxylate

To a solution of methyl2-cyclopropyl-4-oxo-4,5-dihydrofuran-3-carboxylate (24 g, 122 mmol,Step 1) in anhydrous ethanol (200 mL) was added sodium acetate (15.05 g,183 mmol) and NH₂OH.HCl (10.20 g, 147 mmol). The mixture was heated toreflux for 1 hour. The mixture was concentrated under reduced pressureto give a residue that was diluted with water and extracted with ethylacetate. The organic phase was washed with brine, dried over Na₂SO₄, andconcentrated under reduced pressure. The residue was purified bychromatography on silica gel (EtOAc/PE, 1:20-5) to give the titledcompound (3.9 g, yield 15%). ¹H NMR (400 MHz, CDCl₃) δ ppm 4.85 (s, 2H),4.39 (q, J=7.2 Hz, 2H), 2.36-2.23 (m, 1H), 1.40 (t, J=7.1 Hz, 3H), 1.03(br. s., 4H).

Step 3: methyl 3-cyclopropyl-5-formyl-1,2-oxazole-4-carboxylate

To a solution of methyl3-cyclopropyl-5-(hydroxymethyl)-1,2-oxazole-4-carboxylate (3.9 g, 18.46mmol, Step 2) in anhydrous toluene (30 mL) was added MnO₂ (4.82 g, 55.4mmol). The mixture was heated to reflux for 4 hours. The volatiles wereremoved under reduced pressure to give a residue that was purified bycolumn chromatography on silica gel (EtOAc/PE, 1:20-5) to give thetitled compound (3.7 g, yield 96%) that was used directly in the nextstep. LCMS (ESI+) m/z 196.1 (M+H)⁺, retention time 0.581 minute.

Step 4: 3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of methyl 3-cyclopropyl-5-formyl-1,2-oxazole-4-carboxylate(3.7 g, 17.6 mmol, Step 3) in anhydrous ethanol (50 mL) was addedhydrazine hydrate (2.78 ml, 88 mmol) at 0° C. The resulting mixture wasstirred at room temperature for 2 hours. The solid was collected byfiltration and dried to give the titled compound (3.0 g, yield 96%). ¹HNMR (400 MHz, CDCl₃) δ ppm 10.81 (br. s., 1H), 8.23 (s, 1H), 2.48-2.37(m, 1H), 1.31-1.22 (m, 2H), 1.20-1.10 (m, 2H).

Step 5: 7-bromo-3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(4.7 g, 26.5 mmol, Step 4) and LiOH.H₂O (3.18 g, 133 mmol) in CH₃OH (50mL) was added Br₂ (4.10 mL, 80 mmol) at 0° C. The resulting mixture wasstirred at 70° C. for 12 hours. The mixture was concentrated underreduced pressure to give a residue that was poured into H₂O (50 mL). Theresulting mixture was extracted with ethyl acetate. The combined organiclayers were dried over Na₂SO₄ and concentrated to give a residue thatwas purified by column chromatography on silica gel (EtOAc/PE, 1:20-5)to give the titled compound (1.3 g, yield 19%). ¹H NMR (400 MHz, CDCl₃)δ ppm 10.65 (br. s., 1H), 2.47-2.33 (m, 1H), 1.29-1.22 (m, 2H),1.20-1.11 (m, 2H).

Step 6:7-bromo-5-(4-chlorobenzyl)-3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (300 mg,1.17 mmol, Step 5) in N,N-dimethylformamide (5 mL) was added K₂CO₃ (648mg, 4.69 mmol) and 1-chloro-4-(chloromethyl)benzene (283 mg, 1.75 mmol).After stirring at 50° C. for 2 hours, the mixture was diluted with waterand extracted with ethyl acetate. The combined organic phase was washedwith brine and concentrated under reduced pressure to give the titledcompound (270 mg, yield 60%). ¹H NMR (400 MHz, CDCl₃) δ ppm 8.17 (s,1H), 7.36-7.29 (m, 2H), 7.27-7.20 (m, 2H), 5.27 (d, J=13.7 Hz, 2H),2.46-2.36 (m, 1H), 1.22-1.17 (m, 2H), 1.15-1.09 (m, 2H).

Step 7:N-{3-[5-(4-chlorobenzyl)-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-cyclopropyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(270 mg, 0.7 mmol, Step 6) in N,N-dimethylformamide (2 mL) and water(0.5 mL) was added (3-acetamidophenyl)boronic acid (152 mg, 0.85 mmol),K₂CO₃ (245 mg, 1.77 mmol) and tetrakis(triphenylphosphine)palladium(0)(82 mg, 0.071 mmol). After stirring at 80° C. overnight under nitrogen,the mixture was diluted with water and extracted with ethyl acetate. Theorganic phase was washed with brine and concentrated under reducedpressure to give a residue that was purified by preparative HPLC(methodC) to give the titled compound (87 mg, yield 28%). ¹H NMR (400 MHz,DMSO-d₆) δ ppm 10.19 (s, 1H), 8.28 (s, 1H), 7.77 (d, J=8.4 Hz, 1H), 7.67(d, J=7.9 Hz, 1H), 7.47 (t, J=8.2 Hz, 1H), 5.42 (s, 2H), 2.09-2.04 (m,3H), 1.22-1.14 (m, 4H); LCMS (method B) (ESI+) m/z 435.1 (M+H)⁺,retention time 3.568 minutes.

Example 525-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(180 mg, 0.454 mmol, Example 91-Step 6) in N,N-dimethylformamide (2 mL)and water (0.5 mL) was added (2,5-dimethoxyphenyl)boronic acid (99 mg,0.545 mmol), K₂CO₃ (157 mg, 1.134 mmol) andtetrakis(triphenylphosphine)palladium(0) (52.4 mg, 0.045 mmol). Afterstirring at 80° C. overnight under nitrogen, the mixture was dilutedwith water and extracted with ethyl acetate (50 mL×3). The organic phasewas washed with brine and concentrated under reduced pressure. Theresidue was purified by preparative HPLC (method B) to give the titledcompound (68 mg, yield 33%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.38 (d,J=8.4 Hz, 2H), 7.24 (d, J=8.4 Hz, 2H), 7.02-6.89 (m, 3H), 5.34 (s, 2H),3.74 (d, J=4.0 Hz, 6H), 2.96 (t, J=7.5 Hz, 2H), 1.82 (sxt, J=7.4 Hz,2H), 1.02-0.92 (m, 3H); LCMS (method B) (ESI+) m/z 440.2 (M+H)⁻,retention time 3.327 minutes.

Example 533-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzenesulfonamide

The titled compound was prepared using the procedure described inExample 4 substituting (3-sulfamoylphenyl)boronic acid (32 mg, 0.16mmol) for (2,6-difluoropyridin-4-yl)boronic acid. Purification wasachieved by preparative liquid chromatography (Method C, 0.5-8.5 minuteslinear gradient 40-70% A). (46 mg, yield 40%).

¹H NMR (400 MHz,DMSO-d₆/D₂O, Temperature=90° C.) δ ppm 8.52 (t, J=1.8Hz, 1H), 8.28-8.21 (m, 1H), 8.04-7.97 (m, 1H), 7.79 (t, J=7.9 Hz, 1H),7.47-7.43 (m, 2H), 7.40-7.35 (m, 2H), 6.35 (q, J=7.0 Hz, 1H), 2.63 (s,3H), 1.84 (d, J=7.0 Hz, 3H); MS (APCI+) m/z 445 (M+H)⁺.

Example 545-[4-fluoro-3-(trifluoromethyl)benzyl]-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2-methoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-fluoro-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 13%

¹H NMR (400 MHz, CD₃OD): δ 7.82-77 (m, 2H), 7.55-7.52 (m, 1H), 7.44-7.42(m, 1H), 7.19-7.18 (m, 1H), 7.10-7.09 (m, 2H), 5.49 (s, 2H), 3.82 (s,3H), 2.64 (s, 3H).

Example 55N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)methanesulfonamide

Under argon,7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg, 0.217 mmol, Example 39-Step 5) was suspended in toluene andmethanol (2.4 mL, 1:1). 2 M Aqueous sodium bicarbonate (0.163 mL, 0.326mmol) andN-(4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)methanesulfonamide(71.0 mg, 0.217 mmol) were added followed bytetrakis(triphenylphosphine)palladium(0) (25.08 mg, 0.022 mmol). Thereaction mixture was heated with stirring in a Biotage® microwavereactor at 130° C. for 30 minutes. The reaction mixture was thenpartitioned between water and ethyl acetate. The aqueous phase wasextracted twice more with ethyl acetate. The combined organic fractionswere washed with brine, dried over MgSO₄ and then concentrated underreduced pressure. The residue was purified by flash chromatography on aTeledyne Isco CombiFlash® apparatus using a RediSep® silica gelcartridge (4 g) eluted with 0-10% methanol/dichloromethane. The residuewas stirred with a little diisopropyl ether, and the resultantprecipitate was collected and dried in a vacuum oven to give the titledcompound (49 mg, yield 46%).

¹H NMR (600 MHz, DMSO-d₆) δ ppm 9.66 (s, 1H), 7.44-7.37 (m, 5H),7.40-7.33 (m, 1H), 7.29-7.22 (m, 1H), 6.33 (q, J=7.0 Hz, 1H), 3.78 (s,3H), 2.97 (s, 3H), 2.58 (s, 3H), 1.73 (d, J=7.1 Hz, 3H); MS (ESI+) m/z489.2 (M+H)⁺.

Example 565-(4-chlorobenzyl)-3-methyl-7-(thiophen-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added thiophen-2-ylboronic acid (43.2 mg, 0.338 mmol),K₂CO₃ (0.097 g, 0.705 mmol) and tetrakis(triphenylphosphine)palladium(0)(0.033 g, 0.028 mmol). The resulting mixture was stirred at 80° C.overnight under N₂. After cooling down to room temperature, the reactionmixture was concentrated under reduced pressure to give a residue thatwas washed with a mixture of CH₃OH and H₂O to give the titled compound(31 mg, yield 31%). ¹H NMR (CDCl₃, 400 MHz):δ 8.00 (d, J=3.1 Hz, 1H),7.50 (d, J=4.9 Hz, 1H), 7.45 (d, J=8.4 Hz, 2H), 7.31 (d, J=8.4 Hz, 2H),7.19 (dd, J=4.0, 4.9 Hz, 1H), 5.39 (s, 2H), 2.71 (s, 3H). m/z 357.8.

Example 57N-(3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamidophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and1-(bromomethyl)-4-(trifluoromethyl)benzene for 4-(bromomethyl)pyridinein Step 2. Yield 37%

¹H NMR (400 MHz, DMSO): δ 10.18 (br, 1H), 8.28 (s, 1H), 7.80-7.78 (d,J=7.6 Hz, 1H), 7.77-7.60 (m, 3H), 7.59-7.57 (d, J=7.6 Hz, 2H), 7.48-7.44(t, J=7.6 Hz, 1H), 5.50 (s, 2H), 2.59 (s, 3H), 2.06 (s, 3H). m/z 443.2.

Example 585-[(1R)-1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The individual enantiomers of the mixture of Example 114 were separatedby preparative chiral chromatography (WHELK-O® 1 (S,S), 30×250 mmcolumn, 5 μm, concentration of 75 mg/mL in CH₃OH/CH₂Cl₂ (8:2), flow rate75 mL/minute; 20% CH₃OH in CO₂ at 100 psi) 6.89 bar) to afford the titlecompound as the second-eluting enantiomer with a retention time of 8.6minutes. Stereocenter arbitrarily assigned. ¹H NMR (300 MHz, CDCl₃) δppm 7.41-7.35 (m, 2H), 7.31-7.26 (m, 2H), 6.33 (q, J=7.1, 7.1, 7.1 Hz,1H), 2.66 (s, 3H), 2.56 (s, 3H), 1.77 (d, J=7.1 Hz, 3H); MS (DCI/NH₃)m/z 304 (M+H)⁺, 321 (M+NH₄)⁺.

Example 593-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzamide

Under argon,7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(400 mg, 1.085 mmol, Example 39-Step 5) was suspended in toluene andmethanol (12 mL, 1:1). 2 M Aqueous sodium bicarbonate (0.814 mL, 1.628mmol) and4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzamide (301mg, 1.085 mmol) were added followed bytetrakis(triphenylphosphine)palladium(0) (125 mg, 0.109 mmol). Thereaction mixture was heated with stirring in a Biotage® microwavereactor at 130° C. for 30 minutes. The reaction mixture was thenpartitioned between water and ethyl acetate. The aqueous phase wasextracted twice more with ethyl acetate. The combined organic fractionswere washed with brine, dried over MgSO₄ and then concentrated underreduced pressure. The residue was purified by flash chromatography on aTeledyne Isco CombiFlash® apparatus using a RediSep® silica gelcartridge (4 g) eluted with 0-10% methanol/dichloromethane. The residuewas purified with a second flash chromatography on a Teledyne IscoCombiFlash® apparatus using an Agilent silica gel cartridge (8 g) elutedwith 0-8% methanol/dichloromethane to give the titled compound (380 mg,yield 80%).

¹H NMR (600 MHz, DMSO-d₆) δ ppm 8.12-8.07 (m, 1H), 8.03-7.94 (m, 2H),7.41 (s, 4H), 7.38 (s, 1H), 7.31 (d, J=8.8 Hz, 1H), 6.32 (q, J=7.0 Hz,1H), 3.90 (s, OH), 3.85 (s, 3H), 2.59 (s, 3H), 1.75 (d, J=7.1 Hz, 3H);MS (ESI+) m/z 439.1 (M+H)⁺.

Example 605-[2-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

3,7-Dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (100 mg, 0.606 mmol)was dissolved in N,N-dimethylformamide (3 mL) and treated at roomtemperature with sodium hydride (17.44 mg, 0.727 mmol, 29.1 mg as a 60%dispersion in oil) under an argon atmosphere. After 30 minutes,1-(2-bromoethyl)-4-chlorobenzene (133 mg, 0.088 mL, 0.606 mmol) wasadded, and the mixture was stirred for an additional 5 hours at ambienttemperature. The reaction mixture was partitioned between ethyl acetateand water. The aqueous phase was extracted twice more with ethylacetate. The combined organic fractions were washed with brine, driedover MgSO₄, and concentrated under reduced pressure. The residue wastreated with ethyl acetate/diisopropyl ether (1:4), and the precipitatewas collected and dried in a vacuum oven to give the titled compound.

¹H NMR (600 MHz, DMSO-d₆) δ ppm 7.36-7.31 (m, 2H), 7.27-7.21 (m, 2H),4.34-4.28 (m, 2H), 3.01 (dd, J=8.3, 6.7 Hz, 2H), 2.56 (s, 3H), 2.48 (s,3H); MS (ESI+) m/z 304.1 (M+H)⁺.

Example 61N-(2-fluoro-5-{5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamido-4-fluorophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-fluoro-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 17%

¹H NMR (400 MHz, CD₃OD): δ 8.23-8.21 (m, 1H), 7.98-7.96 (d, J=7.9 Hz,1H), 7.58-7.54 (m, 2H), 7.47-7.42 (t, J=8.8 Hz, 1H), 7.27-7.23 (t, J=8.8Hz, 1H), 5.00-4.97 (m, 2H), 2.67 (s, 3H), 1.96 (s, 3H). m/z 479.1.

Example 62N-(2-fluoro-5-{5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamido-4-fluorophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 15%

¹H NMR (400 MHz, CD₃OD): δ 8.19 (s, 1H), 7.92-7.90 (d, J=7.2 Hz, 1H),7.46-7.41 (m, 3H), 7.09-7.07 (d, J=8.8 Hz, 1H), 5.03-5.01 (m, 1H),4.75-4.72 (m, 1H), 3.86 (s, 3H), 2.66 (s, 3H), 1.94 (s, 3H). m/z 491.2.

Example 635-[1-(4-chlorophenyl)ethyl]-7-(5-fluoro-2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg, 0.217 mmol, Example 39-Step 5) was combined with potassiumcarbonate (75.0 mg, 0.543 mmol) and (5-fluoro-2-methoxyphenyl)boronicacid (36.9 mg, 0.217 mmol) in 1,2-dimethoxyethane and water (5 mL, 4:1).Then tetrakis(triphenylphosphine)palladium(0) (25.08 mg, 0.022 mmol) wasadded, and the mixture was heated for 4 hours at 80° C. under an argonatmosphere. The reaction mixture was partitioned between water and ethylacetate. The organic fraction was then washed with brine, dried overMgSO₄, and concentrated under reduced pressure. The residue was purifiedby flash chromatography on a Teledyne Isco CombiFlash® Rf apparatususing a silica gel cartridge (8 g) eluted with 20% ethylacetate/cyclohexane The residue was dried in a vacuum oven overnight togive the titled compound (19 mg, yield 28%).

¹H NMR (500 MHz, DMSO-d₆) δ ppm 7.47-7.38 (m, 1H), 7.41 (s, 3H),7.33-7.23 (m, 2H), 6.30 (q, J=7.0 Hz, 1H), 3.79 (s, 3H), 3.73 (s, OH),2.59 (s, 3H), 1.73 (d, J=7.0 Hz, 3H); MS (ESI+) m/z 414.2 (M+H)⁺.

Example 64N-(4-methoxy-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

Step 2:7-(5-amino-2-methoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl]-[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 64, 120 mg, 0.309 mmol),4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (77 mg,0.309 mmol), sodium carbonate (32.8 mg, 0.309 mmol), and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (226 mg,0.309 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (3 mL) and water(0.3 mL) in a 10-mL sealed tube. The reaction mixture was irradiated ina microwave reactor for 60 minutes at 100° C. The reaction mixture wasthen concentrated under reduced pressure, and the residue was purifiedby silica gel column chromatography eluted with EtOAc/PE (1:2) to givethe titled compound.

Step 3:N-(4-methoxy-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

7-(5-Amino-2-methoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.139 mmol) and triethylamine (14.11 mg, 0.139 mmol) werecombined in dichloromethane (5 mL). Then acetyl chloride (10.94 mg,0.139 mmol) was added, and the resultant reaction mixture was stirred atambient temperature for 1 hour. The mixture was concentrated underreduced pressure, and the residue was purified by reverse phase (C18)column chromatography eluted with methanol/water (9:1) to give thetitled compound. ¹H NMR (300 MHz, CD₃OD) δ ppm 2.15 (s, 3H), 2.67 (s,3H), 3.85 (s, 3H), 5.57 (s, 2H), 7.18 (d, 1H), 7.69 (m, 6H); MS (ESI+)m/z 473.2 (M+H)⁺.

Example 652-amino-6-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamideStep 1:2-amino-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile

To a degassed suspension of 2-amino-6-chlorobenzonitrile (0.25 g, 1.638mmol), bis(pinacolato)diboron (0.416 g, 1.638 mmol), and potassiumacetate (0.241 g, 2.458 mmol) in dioxane (5.0 mL),tricyclohexylphosphine (0.032 g, 0.115 mmol) andtris(dibenzylideneacetone)dipalladium(0) (0.045 g, 0.049 mmol,Pd₂(dba)₃) were added. The mixture was purged with nitrogen for 5minutes and then heated at 120° C. for 2 hours. The mixture was filteredthrough diatomaceous earth, and the cake was washed with ethyl acetate.The filtrate and wash were combined and concentrated. The residue waspurified by silica gel chromatography eluted with 5-40% ethylacetate/hexane to give the titled compound. ¹H NMR (400 MHz, CDCl₃) δppm 1.37 (s, 12H) 4.44 (s, 2H) 6.83 (d, J=8.24 Hz, 1H) 7.18 (d, J=7.16Hz, 1H) 7.27-7.39 (m, 1H).

Step 2:2-amino-6-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamide

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.163 mmol, Example 39-Step 5) was combined with potassiumcarbonate (56.2 mg, 0.407 mmol) and2-amino-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile(47.7 mg, 0.195 mmol, Step 1) in 1,2-dimethoxyethane and water (5 mL,4:1). Then tetrakis(triphenylphosphine)palladium(0) (18.81 mg, 0.016mmol) was added, and the mixture was heated for 4 hours at 80° C. underan argon atmosphere. The reaction mixture was partitioned between waterand ethyl acetate. The organic fraction was then washed with brine,dried over MgSO₄, and concentrated under reduced pressure. The residuewas purified by flash chromatography using a Teledyne Isco CombiFlash®Rf apparatus with a 4 g silica gel cartridge eluted with 30% ethylacetate/cyclohexane. The product containing fractions were combined andconcentrated. The residue was stirred with a small amount of ethylacetate/diisopropyl ether (1:1). The resultant solid was collected byvacuum filtration and was dried in a vacuum oven overnight to give thetitled compound (12 mg, yield 17%).

¹H NMR (500 MHz, DMSO-d₆) δ ppm 7.51 (s, 1H), 7.43-7.35 (m, 4H), 7.24(t, J=7.8 Hz, 1H), 7.17 (s, 1H), 6.92 (ddd, J=17.3, 7.8, 1.0 Hz, 2H),6.22 (q, J=7.0 Hz, 1H), 5.42 (s, 2H), 3.31 (s, 1H), 2.58 (s, 3H), 1.72(d, J=7.1 Hz, 3H); MS (ESI+) m/z 424.1 (M+H)⁺.

Example 667-(4-fluorophenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 19, 100 mg, 0.408 mmol) in N,N-dimethylformamide (2 mL) wasadded NaH (14.68 mg, 0.612 mmol). The mixture was stirred at roomtemperature for 15 minutes, and then4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene (132 mg, 0.489mmol) was added. The mixture was stirred at room temperature overnight.The solid was collected by filtration and washed with water and methanolto give the titled compound (98 mg, yield 55%).

¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.51 (m, 2H), 8.09-8.05 (m, 2H),7.45-7.40 (m, 2H), 7.31-7.30 (m, 2H), 5.47 (s, 2H), 2.59 (s, 3H); MS(APCI⁺) m/z 434.0 (M+H)⁺.

Example 675-(4-chlorobenzyl)-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (2-methoxyphenyl)boronic acid (51.4 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 54%

1H NMR (CDCl3, 400 MHz):δ 7.48-7.56 (m, 1H), 7.37-7.47 (m, 3H), 7.31 (d,J=8.38 Hz, 2H), 7.00-7.15 (m, 2H), 5.40 (s, 2H), 3.84 (s, 3H), 2.68 (s,3H). m/z 381.8.

Example 685-[(1S)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

5-[1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-onewas synthesized in analogy to Example 1. The enantiomers were separatedby supercritical fluid chromatography to give the titled compound Themobile phase was comprised of supercritical CO₂ supplied by a bulk tankof 99.5% bone-dry non-certified CO₂ pressurized to 1200 psi (82.7 bar)with a modifier of methanol (0.1 N NH₄OH) at a flow rate of 70 g/minute.UV detection was set to collect at a wavelength of 220 nm, the columnwas heated to 35° C., and the backpressure regulator was set to maintain100 bar. The sample was dissolved in methanol at a concentration ofabout 50 mg/mL, and the injection volume was 1 mL. The mobile phase washeld isocratically at 40% methanol (0.1 N NH₄OH):CO2. The instrument wasfitted with a Chiralpak® AS-H 5 μm, 30 mm×250 mm column. ¹H NMR (400MHz, DMSO-d₆) δ ppm 7.39 (s, 3H), 7.17-7.08 (m, 2H), 6.92 (d, J=2.6 Hz,1H), 6.30 (q, J=6.9 Hz, 1H), 3.71 (d, J=7.1 Hz, 6H), 2.46-2.39 (m, 1H),1.71 (d, J=7.1 Hz, 3H), 1.14 (d, J=7.5 Hz, 4H).

Example 695-[4-chloro-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting4-(bromomethyl)-1-chloro-2-(trifluoromethyl)benzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 60-100% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.83 (d, J=2.1Hz, 1H), 7.69 (d, J=8.3 Hz, 1H), 7.58 (dd, J=8.4, 2.1 Hz, 1H), 5.38 (s,2H), 2.57 (s, 3H), 2.51 (s, 3H); MS (APCI⁺) m/z 358.0 (M+H)+.

Example 70N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (3-acetamidophenyl)boronic acid (60.5 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 56%

¹H NMR (CDCl₃, 400 MHz):δ 8.11 (s, 1H), 7.83 (d, J=7.94 Hz, 1H), 7.72(d, J=7.94 Hz, 1H), 7.31-7.49 (m, 3H), 7.25 (d, J=8.38 Hz, 3H), 5.37 (s,2H), 2.64 (s, 3H), 2.17 (s, 3H). m/z 408.8.

Example 715-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.18 g, 0.468 mmol, Example 27-Step 6) in 1,4-dioxane(15 mL) and water(5 mL) was added (2,5-dimethoxyphenyl)boronic acid (0.085 g, 0.46 mmol),K₂CO₃ (0.16 g, 1.17 mmol) and tetrakis(triphenylphosphine)palladium(0)(0.054 g, 0.047 mmol). After stirring at 80° C. overnight, the mixturewas diluted with water and extracted with ethyl acetate (50 mL×3). Theorganic phase was washed with brine and concentrated under reducedpressure to furnish a residue that was purified by preparative HPLC(method B) to give the titled compound (40.6 mg, yield 19%). ¹H NMR (400MHz, CDCl₃) δ ppm 7.46 (d, J=7.9 Hz, 2H), 7.32 (d, J=8.4 Hz, 2H),7.09-6.98 (m, 3H), 5.42 (s, 2H), 4.94 (s, 2H), 3.82 (d, J=6.6 Hz, 7H),3.56 (s, 3H).

Example 72N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

Example 78 (500 mg, 1.064 mmol) was separated by chiral super criticalfluid chromatography (method A) to give recovered racemic material (50.6mg, yield 11.2%), the titled compound (162.9 mg, yield 36.2%) and theenantiomer (208 mg, yield 46.2%, Example 34). ¹H NMR (400 MHz,methanol-d₄) δ ppm 8.37 (s, 1H), 7.75 (d, J=7.2 Hz, 1H), 7.59 (d, J=8.0Hz, 1H), 7.40-7.33 (m, 3H), 7.24 (d, J=8.0 Hz, 2H), 6.30 (q, J=6.8 Hz,1H), 2.54 (s, 3H), 2.08 (s, 3H), 1.79 (d, J=7.2 Hz, 3H); LCMS (method C)(ESI+) m/z 423 (M+H)⁺, retention time 3.364 minutes.

Example 733-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzoicacid

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg, 0.217 mmol, Example 39-Step 5) in ethanol/toluene (1:1, 2.4 mL)was combined with 2 M aqueous sodium carbonate (0.163 mL, 0.326 mmol)and 4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoicacid (60.4 mg, 0.217 mmol). Thentetrakis(triphenylphosphine)palladium(0) (25.08 mg, 0.022 mmol) wasadded, and the mixture was heated in a Biotage® microwave reactor for 30minutes at 130° C. under an argon atmosphere. The reaction mixture waspartitioned between water and ethyl acetate. The aqueous phase wasextracted twice more with ethyl acetate. The combined organic fractionswere then washed with brine, dried over MgSO₄, and concentrated underreduced pressure. The residue was purified by flash chromatography on aTeledyne Isco CombiFlash® apparatus using a silica gel cartridge (4 g)eluted with 10% methanol/dichloromethane. The residue was stirred in asmall amount of diisopropyl ether, and the precipitate was collected togive the titled compound (19 mg, yield 20%). ¹H NMR (600 MHz, DMSO-d₆) δppm 12.94 (s, 1H), 8.13 (dd, J=8.7, 2.2 Hz, 1H), 8.03 (d, J=2.2 Hz, 1H),7.41 (s, 4H), 6.33 (q, J=7.0 Hz, 1H), 3.87 (s, 3H), 2.59 (s, 3H), 1.74(d, J=7.1 Hz, 3H); MS (ESI+) m/z 440.1 (M+H)⁺.

Example 747-(4-fluorophenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 19, 100 mg, 0.408 mmol) in N,N-dimethylformamide (2 mL) wasadded NaH (14.68 mg, 0.612 mmol). The mixture was stirred at roomtemperature for 15 minutes, and then 4-(bromomethyl)pyridinehydrobromide (124 mg, 0.489 mmol) was added. The solid was collected byfiltration and washed with water and methanol to give the titledcompound (18 mg, yield 13%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.09-8.06(m, 2H), 7.68-7.65 (m, 2H), 7.45-7.41 (m, 2H), 7.22 (m, 1H), 5.41 (s,2H), 3.84 (s, 3H), 2.59 (s, 3H); MS (APCI⁺) m/z 434.0 (M+H)⁻.

Example 755-[(R)-(4-chlorophenyl)(phenyl)methyl]-3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The racemic parent structure could be prepared as described in Example114-Step 2 substituting3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one for3,7-dimethyl-[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one and1-[bromo(phenyl)methyl]-4-chlorobenzene for1-(1-bromoethyl)-4-chlorobenzene. The individual enantiomers of themixture were separated by preparative chiral chromatography (Chiralpak®AD-H, 21×250 mm column, 5 μm, concentration of 15 mg/mL in CH₃OH, flowrate 70 mL/minute CH₃OH, 20% CH₃OH/CO₂, 150 psi=10.34 bar) to afford thetitled compound as the second-eluting enantiomer (relative to Example89) with a retention time of 2.122 minutes, 94% ee. Stereocenterarbitrarily assigned. MS (ESI⁺) m/z 394 (M+H)⁺.

Example 765-(4-chlorobenzyl)-3-methyl-7-(2-methylphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added o-tolylboronic acid (46.0 mg, 0.338 mmol), K₂CO₃(0.097 g, 0.705 mmol) and tetrakis(triphenylphosphine)palladium(0)(0.033 g, 0.028 mmol). The resulting mixture was stirred at 80° C.overnight under N₂. After cooling down to room temperature, the reactionmixture was concentrated under reduced pressure to give a residue thatwas washed with a mixture of CH₃OH and H₂O to give the titled compound.Yield 35%

¹H NMR (DMSO, 400 MHz): δ 7.52 (d, J=7.50 Hz, 1H), 7.33-7.48 (m, 7H),5.39 (s, 2H), 2.60 (s, 3H), 2.23 (s, 3H). m/z 365.8.

Example 777-(2-amino-3,5-difluorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting 2,4-difluoro-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline for methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® Rf apparatus using asilica gel cartridge (4 g) eluted with 25% ethyl acetate/cyclohexane.The residue was triturated with a little ethyl acetate/diisopropyl ether(1:1), and the solid was dried overnight in a vacuum oven to give thetitled compound (35 mg, yield 52%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm7.44-7.31 (m, 6H), 6.37 (q, J=7.0 Hz, 1H), 5.68 (s, 2H), 2.62 (s, 3H),1.75 (d, J=7.0 Hz, 3H); MS (ESI+) m/z 417.1 (M+H)⁺.

Example 78N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The reactions were conducted in parallel (different scale) but combinedfor purification.

The first batch: To a solution of7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(40 mg, 0.109 mmol, Example 39-Step 5) and (3-acetamidophenyl)boronicacid (38.8 mg, 0.217 mmol) in 1,2-dimethoxyethane:water (1.25 mL, 4:1),were added potassium carbonate (37.5 mg, 0.271 mmol) andtetrakis(triphenylphosphine)palladium(0) (12.54 mg, 10.85 μmol). Thenthe reaction mixture was stirred at 100° C. under a nitrogen atmosphereovernight. Then the reaction mixture was concentrated under reducedpressure, and the aqueous mixture was extracted with ethyl acetate. Theorganic phase was dried and concentrated. The residue was purified bypreparative thin layer chromatography on silica gel and eluted withEtOAc/PE to give crude titled compound.

The second batch: To a solution of7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(180 mg, 0.488 mmol, Example 39-Step 5) and (3-acetamidophenyl)boronicacid (175 mg, 0.977 mmol) in 1,2-dimethoxyethane:water (5 mL, 4:1), wereadded potassium carbonate (169 mg, 1.221 mmol) andtetrakis(triphenylphosphine)palladium(0) (56.4 mg, 0.049 mmol). Then thereaction mixture was stirred at 90° C. under a nitrogen atmosphereovernight. The reaction mixture was concentrated under reduced pressure,and the residue was purified by preparative thin layer chromatography onsilica gel and eluted with EtOAc/PE to give crude titled compound.

The third batch: To a solution of7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(500 mg, 1.221 mmol, Example 39-Step 5) and (3-acetamidophenyl)boronicacid (328 mg, 1.831 mmol) in 1,2-dimethoxyethane:water (20 mL, 4:1),were added potassium carbonate (422 mg, 3.05 mmol) andtetrakis(triphenylphosphine)palladium(0) (141 mg, 0.122 mmol). Then thereaction mixture was stirred at 90° C. under nitrogen overnight. Thenthe reaction mixture was concentrated under reduced pressure, and theresidue was purified by column chromatography on silica gel(EtOAc/PE=1:5-1:2) to give crude titled compound.

The fourth batch: To a solution of7-bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(1.7 g, 4.15 mmol, Example 39-Step 5) and (3-acetamidophenyl)boronicacid (1.114 g, 6.23 mmol) in 1,2-dimethoxyethane:water (50 mL, 4:1),were added potassium carbonate (1.434 g, 10.38 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.480 g, 0.415 mmol). Then thereaction mixture was stirred at 90° C. under nitrogen overnight. Thereaction mixture was concentrated under reduced pressure, and theresidue was purified by column chromatography on silica gel(EtOAc/PE=1:5˜1:2) to give crude titled compound.

The above crude products in four batches were combined, and then furtherpurified by preparative high performance liquid chromatography (methodA) to give the titled compound (500 mg, yield 17.9%). ¹H NMR (400 MHzCDCl₃) δ ppm 8.18 (s, 1H), 7.83 (d, J=7.6 Hz, 1H), 7.67 (d, J=8.0 Hz,1H), 7.45-7.39 (m, 3H), 7.25-7.23 (m, 3H), 6.36 (q, J=7.2 Hz, 1H), 2.64(s, 3H), 2.19 (s, 3H), 1.82 (d, J=7.2 Hz, 3H); LCMS (method B) (ESI+)m/z 423 (M+H)⁺, retention time 3.038 minutes.

Example 795-[1-(4-chlorophenyl)ethyl]-7-[2-methoxy-5-(trifluoromethyl)phenyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg, 0.217 mmol, Example 39-Step 5) in ethanol/toluene (1:1, 2 mL)was combined with M aqueous sodium carbonate (0.163 mL, 0.326 mmol) and((2-methoxy-5-(trifluoromethyl)phenyl)boronic acid (47.7 mg, 0.217mmol). Then tetrakis(triphenylphosphine)palladium(0) (25.08 mg, 0.022mmol) was added, and the mixture was heated in a CEM microwave reactorfor 30 minutes at 130° C. under an argon atmosphere. The reactionmixture was partitioned between water and ethyl acetate. The organicfraction was then washed with brine, dried over MgSO₄, and concentratedunder reduced pressure. The residue was purified by flash chromatographyon a Teledyne Isco CombiFlash® Rf apparatus using a silica gel cartridge(4 g) eluted with 20% ethyl acetate/cyclohexane. The titled compound wasobtained after drying overnight in a vacuum oven (16 mg, yield 16%). ¹HNMR (600 MHz, DMSO-d₆) δ ppm 7.53 (d, J=8.7 Hz, 1H), 7.41-¹H NMR (600MHz, DMSO-d₆) δ ppm 7.95 (ddd, J=8.8, 2.5, 0.8 Hz, 1H), 7.74 (d, J=2.6Hz, 1H), 7.45 (d, J=8.7 Hz, 1H), 7.41 (s, 3H), 6.31 (q, J=7.0 Hz, 1H),3.89 (s, 3H), 2.59 (s, 3H), 1.73 (d, J=7.1 Hz, 3H), 1.40 (s, 3H), 1.09(s, 2H); MS (ESI+) m/z 464.1 (M+H)⁺.

Example 805-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(120 mg, 0.288 mmol, Example 107-Step 6) in 1,2-dimethoxyethane (4 mL)and water (1 mL) was added (2,5-dimethoxyphenyl)boronic acid (62.9 mg,0.346 mmol), K₂CO₃ (100 mg, 0.720 mmol) andtetrakis(triphenylphosphine)palladium(0) (33.3 mg, 0.029 mmol). Themixture was stirred at 80° C. under N₂ overnight. The mixture wasdiluted with water and extracted with ethyl acetate. The organic phasewas washed with brine and concentrated under reduced pressure. Theresidue was washed with methanol and dried to give the titled compound(113 mg, yield 83%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.24 (d, J=7.06 Hz,2H), 7.49-7.65 (m, 3H), 7.41 (s, 4H) 7.08-7.24 (m, 2H), 7.04 (d, J=2.65Hz, 1H), 5.43 (s, 2H), 3.75 (d, J=2.21 Hz, 6H); LCMS (method E) (ESI+)m/z 474.1(M+H)⁺, retention time 3.241 minutes.

Example 817-(2,5-dimethoxyphenyl)-5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2,5-dimethoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-fluoro-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 35%.

¹H NMR (CDCl₃, 400 MHz):δ 7.93 (br. s, 2H), 7.37-7.49 (m, 3H), 7.31 (d,J=8.38 Hz, 3H), 5.44 (s, 2H), 2.71 (s, 3H), 2.47 (s, 3H). m/z 365.8.

Example 823-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamideStep 1:7-bromo-5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-(one)

7-bromo-5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-(one)was separated by SFC chiral chromatography (3.58 g, column: Whelk-O1(S,S)(Regis Technologies), Liquid phase: 5-50% MeOH:CO2 10 min @ 3ml/min, 150 bar to give7-bromo-5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-(one)(1554 mg

Rotation value [α]=+144.9° in MeOH (c=3.33 mg/1 ml, Peak A: RT=2.466min, 99.6% ee) and(R)-7-bromo-5-(1-(4-chlorophenypethyl)-3-methylisoxazolo[4,5-d]pyridazin-4(5H)-one(1454 mg, rotation value [α]=−129.7° in MeOH (c=3.92 mg/1, Peak B:RT=4.149 min, 96.7% ee).

Step 2:3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-(methylbenzaminde)

Under argon,7-bromo-5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(300 mg, 0.81 mmol) was suspended in toluene and ethanol (6 ml, 1:1). 2M Aqueous sodium bicarbonate (0.6 ml, 1.22 mmol) and4-methoxy-N-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzamide(237 mg, 0.81 mmol, Example 119-Step 1) were added followed bytetrakis(triphenylphosphine)palladium(0) (94 mg, 0.08 mmol). Thereaction mixture was heated under stirring in a CEM microwave reactor at130° C. for 30 minutes. The reaction mixture was then partitionedbetween water and ethyl acetate. The organic fraction was washed withbrine, dried over MgSO₄ and then concentrated under reduced pressure.The residue was purified by flash chromatography on a Teledyne IscoCombiFlash® Rf apparatus using a silica gel cartridge (12 g) eluted with50% ethyl acetate/heptane. The residue was stirred with diisopropylether, and the solid was collected by vacuum filtration and dried in avacuum oven overnight. A second flash chromatography was performed onthe material in the mother liquor on a Teledyne Isco CombiFlash® Rfapparatus using a silica gel cartridge (4 g, 15 μm) eluted with 50%ethyl acetate/heptane was performed. The residue was stirred withdiisopropyl ether and collected by vacuum filtration. The two solidbatches were combined and dried in a vacuum oven overnight to give thetitled compound (40 mg, yield 11%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm 8.46(q, J=4.6 Hz, 1H), 8.05 (dd, J=8.7, 2.2 Hz, 1H), 7.95 (d, J=2.2 Hz, 1H),7.41 (s, 4H), 7.32 (d, J=8.8 Hz, 1H), 6.33 (q, J=7.0 Hz, 1H), 3.60 (p,J=6.1 Hz, 0H), 2.79 (d, J=4.5 Hz, 3H), 2.59 (s, 2H), 1.75 (d, J=7.0 Hz,4H), 1.04 (d, J=6.0 Hz, 3H); MS (ESI+) m/z 453.0 (M+H)⁺; [α]=+20° (c=1mg/mL, CH₃OH)

Example 835-(4-chlorobenzyl)-7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(100 mg, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added 4-fluorophenylboronic acid (47 mg, 0.338 mmol),potassium carbonate (97 mg, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (33 mg, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling to room temperature, the reaction mixture was concentrated underreduced pressure to get a residue that was washed with a mixture ofmethanol and water to give the titled compound, 68 mg (65%). ¹11NMR (400MHz, CDCl₃) δ ppm 8.16-8.13 (m, 2H), 7.44-7.42 (m, 2H), 7.32-7.30 (m,2H), 7.24-7.20 (m, 2H), 5.43 (s, 2H), 2.71 (s, 3H); LCMS (method F)(ESI+) m/z 369.8 (M+H)⁺.

Example 845-(3-chloro-4-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 4-(bromomethyl)-2-chloro-1-fluorobenzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 50-80% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.52 (dd, J=7.1,2.1 Hz, 1H), 7.37 (t, J=8.9 Hz, 1H), 7.32 (ddd, J=8.5, 4.9, 2.1 Hz, 1H),5.29 (s, 2H), 2.57 (s, 3H), 2.51 (s, 3H); MS (APCI⁺) m/z 308.0 (M+H)⁺.

Example 85N-(3-{5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamidophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and2-(bromomethyl)-1-fluoro-4-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 36%.

¹H NMR (400 MHz, DMSO): δ 10.18 (br, 1H), 8.29 (s, 1H), 7.84-7.76 (m,3H), 7.64-7.62 (d, J=7.6 Hz, 1H), 7.51-7.44 (m, 2H), 5.53 (s, 2H), 2.60(s, 3H), 2.06 (s, 3H). m/z 461.2.

Example 867-(2-aminopyridin-3-yl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.163 mmol, Example 39-Step 5) was combined with potassiumcarbonate (56.2 mg, 0.407 mmol) and3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridin-2-amine (43.0 mg,0.195 mmol) in 1,2-dimethoxyethane and water (5 mL, 4:1). Thentetrakis(triphenylphosphine)palladium(0) (18.81 mg, 0.016 mmol) wasadded, and the mixture was heated for 4 hours at 80° C. under an argonatmosphere. The reaction mixture was partitioned between water and ethylacetate. The organic fraction was then washed with brine, dried overMgSO₄, and concentrated under reduced pressure. The residue was purifiedby flash chromatography using a Teledyne Isco CombiFlash® Rf apparatuswith a 4 g silica gel cartridge eluted with 40% ethylacetate/cyclohexane. The product containing fractions were combined andconcentrated. The residue was stirred with a small amount of ethylacetate/diisopropyl ether (1:1), and the solid was dried in a vacuumoven overnight to give the titled compound (22 mg, yield 35%). ¹H NMR(600 MHz, DMSO-d₆) δ ppm 8.13-8.05 (m, 2H), 7.44-7.37 (m, 4H), 6.76 (dd,J=7.7, 4.8 Hz, 1H), 6.65 (s, 2H), 6.37 (q, J=7.0 Hz, 1H), 3.36-3.31 (m,0H), 2.62 (s, 3H), 1.76 (d, J=7.0 Hz, 3H), 1.04 (d, J=6.1 Hz, OH); MS(ESI+) m/z 382.0 (M+H)⁺.

Example 875-(4-chlorobenzyl)-7-(2,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (2,4-dimethoxphenyl)boronic acid (61.5 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 28%.

¹H NMR (CDCl₃, 400 MHz):δ 7.37 (d, J=8.38 Hz, 2H), 7.21-7.32 (m, 3H),6.50-6.58 (m, 2H), 5.32 (s, 2H), 3.81 (s, 3H), 3.76 (s, 3H), 2.61 (s,3H). m/z 411.8.

Example 885-(5-chloro-2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 2-(bromomethyl)-4-chloro-1-fluorobenzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 50-80% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.42 (ddd,J=8.8, 4.5, 2.8 Hz, 1H), 7.33-7.25 (m, 2H), 5.34 (s, 2H), 2.57 (s, 3H),2.50 (s, 3H). MS (APCI⁻) m/z 308.0 (M+H)⁺.

Example 895-[(S)-(4-chlorophenyl)(phenyl)methyl]-3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The racemic parent structure could be prepared as described in Example114-Step 2 substituting3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one for3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one and1-[bromo(phenyl)methyl]-4-chlorobenzene for1-(1-bromoethyl)-4-chlorobenzene. The individual enantiomers of themixture were separated by preparative chiral chromatography (Chiralpak®AD-H, 21×250 mm column, 5 μm, concentration of 15 mg/mL in CH₃OH, flowrate 70 mL/minute CH₃OH, 20% CH₃OH/CO₂, 150 psi=10.34 bar) to afford thetitled compound as the first-eluting enantiomer (relative to Example 75)with a retention time of 1.837 minutes, 99% ee. Stereocenter arbitrarilyassigned. MS (ESI⁺) m/z 394 (M+H)⁺.

Example 905-(4-chlorobenzyl)-7-(3,5-difluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (3,5-difluorophenyl)boronic acid (53.4 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 21%.

¹H NMR (DMSO, 400 MHz):δ 7.72 (d, J=6.62 Hz, 2H) 7.32-7.55 (m, 5H) 5.45(s, 2H) 2.61 (s, 3H). m/z 387.8.

Example 91N-{3-[5-(4-chlorobenzyl)-4-oxo-3-propyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamideStep 1: methyl 4-oxo-2-propyl-4,5-dihydrofuran-3-carboxylate

To a solution of magnesiumethanolate (8.68 g, 76 mmol) in toluene (50mL) cooled in an ice bath was added ethyl 3-oxohexanoate (12 g, 76 mmol)dropwise. The mixture was stirred at room temperature for 1 hour.Anhydrous acetonitrile (5 mL) was added to the mixture at −10° C.,followed by the slow addition of 2-chloroacetyl chloride (10.28 g, 91mmol). The mixture was allowed to warm to room temperature and left tostir for 2 hours. A diluted solution of sulfuric acid (0.8 mL acid in 28mL ice/water) was added followed by extraction with tert-butyl methylether. The combined organic fractions were dried over Na₂SO₄ andfiltered. The filtrate was cooled to 0° C. A solution of triethylamine(23.33 g, 231 mmol) in tert-butylmethyl ether (50 mL) was added. Thereaction mixture was left to stir at room temperature overnight. Themixture was diluted with water and extracted with dichloromethane (200mL×3). The organic phase was concentrated under reduced pressure. Theresidue was purified by column chromatography on silica gel and elutedwith EtOAc/PE to give the titled compound (9.3 g, yield 62%).

Step 2: methyl 5-(hydroxymethyl)-3-propyl-1,2-oxazole-4-carboxylate

To a solution of methyl 4-oxo-2-propyl-4,5-dihydrofuran-3-carboxylate(9.21 g, 46.5 mmol, Step 1 in anhydrous ethanol (100 mL) was addedsodium acetate (5.72 g, 69.7 mmol) and NH₂OH.HCl (3.87 g, 55.8 mmol).The mixture was heated to reflux for 1 hour. The solvent was removedunder reduced pressure to give a residue that was diluted with water andextracted with ethyl acetate (200 mL×3). The organic phase was washedwith brine, dried over Na₂SO₄, and concentrated under reduced pressure.The residue was purified by column chromatography on silica gel(EtOAc/PE, 1:20-5) to give the titled compound (4.25 g, yield 42%).

Step 3: methyl 5-formyl-3-propyl-1,2-oxazole-4-carboxylate

To a solution of methyl5-(hydroxymethyl)-3-propyl-1,2-oxazole-4-carboxylate (4.25 g, 19.93mmol, Step 2) in anhydrous toluene (100 mL) was added MnO₂ (5.20 g, 59.8mmol). The mixture was heated to reflux for 6 hours. The reactionmixture was concentrated under reduced pressure. The residue waspurified by column chromatography on silica gel (EtOAc/PE, 1:20-5) togive the titled compound (3.6 g, yield 86%).

Step 4: 3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of methyl 5-formyl-3-propyl-1,2-oxazole-4-carboxylate (3.6g, 17.04 mmol, Step 3) in anhydrous ethanol (50 mL) was added hydrazinehydrate (2.67 mL, 85 mmol) 0° C. The resulting mixture was stirred atroom temperature for 2 hours. The solid was collected by filtration anddried to give the titled compound (2.8 g, yield 92%). ¹H NMR (400 MHz,CDCl₃) δ ppm 8.41-8.08 (m, 1H), 6.41-6.30 (m, 1H), 3.13-2.76 (m, 2H),2.07-1.65 (m, 2H), 1.13-0.91 (m, 3H).

Step 5: 7-bromo-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (2.8 g,15.63 mmol, Step 4) and LiOH.H₂O (3.28 g, 78 mmol) in methanol (50 mL)was added Br₂ (2.41 mL, 46.9 mmol) at 0° C. The resulting mixture wasstirred at 70° C. for 12 hours. The volatiles were removed under reducedpressure. The residue was poured into H₂O and extracted with ethylacetate (100 mL×3). The combined organic layers were dried over Na₂SO₄and concentrated in vacuum. The residue was purified by columnchromatography on silica gel (EtOAc/PE, 1:20-5) to give the titledcompound (1.5 g, yield 37%). ¹H NMR (400 MHz, CDCl₃) δ ppm 10.85 (br.s., 1H), 2.96 (t, J=7.7 Hz, 2H), 1.82 (sxt, J=7.4 Hz, 2H), 1.02-0.87 (m,3H).

Step 6: 7-bromo-5-(4-chlorobenzyl)-3-propyl[1,2]oxazol0[4,5-d]pyridazin-4(5H)-one

To a solution of: 7-bromo-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(400 mg, 1.550 mmol, Step 5) in N,N-dimethylformamide (10 mL) was addedK₂CO₃ (857 mg, 6.20 mmol) and 1-chloro-4-(chloromethyl)benzene (374 mg,2.325 mmol). After stirring at 50° C. for 2 hours, the mixture wasdiluted with water and extracted with ethyl acetate (50 mL×3). Thecombined organic phase was washed with brine and concentrated underreduced pressure to give the titled compound (400 mg, yield 67%) whichwas used directly for the next step.

Step 7:N-{3-[5-(4-chlorobenzyl)-4-oxo-3-propyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(180 mg, 0.454 mmol, Step 6) in N,N-dimethylformamide (2 mL) and water(0.5 mL) was added (3-acetamidophenyl)boronic acid (97 mg, 0.545 mmol),K₂CO₃ (157 mg, 1.134 mmol) and tetrakis(triphenylphosphine)palladium(0)(52.4 mg, 0.045 mmol). After stirring at 80° C. overnight undernitrogen, the mixture was diluted with water and extracted with ethylacetate (50 mL×3). The organic phase was washed with brine andconcentrated under reduced pressure. The residue was purified bypreparative HPLC (method C) to give the titled compound (61 mg, yield29%). ¹H NMR (400 MHz, CDCl₃) δ ppm 8.11 (s, 1H), 7.83 (d, J=7.9 Hz,1H), 7.71 (d, J=7.5 Hz, 1H), 7.48-7.35 (m, 3H), 7.33-7.22 (m, 3H), 5.37(s, 2H), 3.07-2.90 (m, 2H), 2.17 (s, 3H), 1.82 (sxt, J=7.4 Hz, 2H),1.06-0.91 (m, 3H); LCMS (method B) (ESI+) m/z 437.1 (M+H)⁻, retentiontime 3.319 minutes.

Example 92 5-(4-chloro-2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 1-(bromomethyl)-4-chloro-2-fluorobenzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 50-80% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.43 (dd,J=10.0, 2.0 Hz, 1H), 7.30 (t, J=8.1 Hz, 1H), 7.25 (dd, J=8.4, 2.0 Hz,1H), 5.33 (s, 2H), 2.57 (s, 3H), 2.49 (s, 3H); MS (APCI⁺) m/z 308.0(M+H)⁺.

Example 937-(2,5-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2,5-dimethoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1. Yield 14%.

¹H NMR (400 MHz, CD₃OD): δ8.78 (s, 2H), 7.97-7.96 (m, 2H), 7.12 (s, 2H),7.05 (s, 1H), 5.74 (s, 2H), 3.79 (s, 6H), 2.64 (s, 3H). m/z 379.0.

Example 94N-{2-fluoro-5-[3-methyl-4-oxo-5-(pyridin-4-ylmethyl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamido-4-fluorophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1. Yield 16%.

¹H NMR (400 MHz, DMSO): δ 9.92 (br, 1H), 8.76 (s, 2H), 8.64-8.62 (d,J=6.8 Hz, 1H), 7.79-7.77 (m, 3H), 7.49-7.44 (m, 1H), 5.66 (s, 2H), 2.60(s, 3H), 2.11 (s, 3H). m/z 394.2.

Example 957-(2,5-dimethoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2,5-dimethoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and1-(bromomethyl)-4-(trifluoromethyl)benzene for 4-(bromomethyl)pyridinein Step 2. Yield 26%.

1H NMR (400 MHz, CD₃OD): δ7.66-7.64 (d, J=8.0 Hz, 2H), 7.60-7.58 (d,J=8.4 Hz, 2H), 7.10 (s, 2H), 7.00 (s,1H), 5.52 (s, 2H), 3.78 (s, 3H),3.77 (s, 3H), 2.63 (s, 3H). m/z 446.0.

Example 96N-{3-[5-(4-chlorobenzyl)-4-oxo-3-(propan-2-yl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamideStep 1: methyl 4-oxo-2-(propan-2-yl)-4,5-dihydrofuran-3-carboxylate

To a solution of magnesiumethanolate (23.81 g, 208 mmol) in toluene (150mL) chilled in an ice bath was added ethyl 4-methyl-3-oxopentanoate (25g, 173 mmol) dropwise. The mixture was stirred at room temperature for 1hour. Anhydrous acetonitrile (150 mL) was added to the mixture at −10°C. followed by the slow addition of 2-chloroacetyl chloride (19.59 g,173 mmol). The mixture was allowed to warm to room temperature and leftto stir for 2 hours. A diluted solution of sulfuric acid was addedfollowed by extraction with tert-butylmethyl ether. The combined organicphase was dried over Na₂SO₄ and filtered. The filtrate was cooled to 0°C. A solution of triethylamine (48.3 ml, 347 mmol) in tert-butylmethylether (100 mL) was added. The reaction mixture was stirred at roomtemperature overnight. The mixture was diluted with water and extractedwith dichloromethane. The organic phase was concentrated under reducedpressure to supply a residue that was purified by chromatography onsilica gel and eluted with EtOAc/PE to give the titled compound (28 g,yield 88%). ¹H NMR (400 MHz, CDCl₃) δ ppm 4.56 (s, 2H), 4.27 (q, J=7.1Hz, 2H), 3.86 (td, J=7.0, 13.8 Hz, 1H), 1.31 (t, J=7.3 Hz, 3H), 1.24 (d,J=7.1 Hz, 6H).

Step 2: methyl5-(hydroxymethyl)-3-(propan-2-yl)-1,2-oxazole-4-carboxylate

To a solution of methyl4-oxo-2-(propan-2-yl)-4,5-dihydrofuran-3-carboxylate (28 g, 141 mmol,Step 1) in anhydrous ethanol (150 mL) was added sodium acetate (17.38 g,212 mmol) and NH₂OH.HCl (11.78 g, 170 mmol). The mixture was heated toreflux for 1 hour. The solvent was removed under reduced pressure togive a residue that was diluted with water and extracted with ethylacetate. The organic phase was washed with brine, dried over Na₂SO₄, andconcentrated in vacuum. The residue was purified by columnchromatography on silica gel (EtOAc/PE, 1:20-5) to give the titledcompound (19 g, yield 63%) which was used directly in the next step.

Step 3: methyl 5-formyl-3-(propan-2-yl)-1,2-oxazole-4-carboxylate

A mixture of methyl5-(hydroxymethyl)-3-(propan-2-yl)-1,2-oxazole-4-carboxylate (4.25 g,19.93 mmol, Step 2) and MnO₂ (23.24 g, 267 mmol) in anhydrous toluene(100 mL) was heated to reflux for 6 hours. The volatiles were removedunder reduced pressure. The residue was purified by columnchromatography on silica gel (EtOAc/PE, 1:20-5) to give the titledcompound (10 g, yield 53%). ¹H NMR (400 MHz, CDCl₃) δ ppm 10.36 (s, 1H),4.47 (q, J=7.1 Hz, 2H), 3.59-3.49 (m, 1H), 1.45 (t, J=7.3 Hz, 3H), 1.40(d, J=6.6 Hz, 6H).

Step 4: 3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of methyl5-formyl-3-(propan-2-yl)-1,2-oxazole-4-carboxylate (10 g, 47.3 mmol,Step 3) in anhydrous ethanol (100 mL) was added hydrazine hydrate (7.43mL, 237 mmol) at 0° C. The resulting mixture was stirred at roomtemperature for 2 hours. The solid was collected by filtration and driedto give the titled compound (4.1 g, yield 48%) which was used directlyin the next step. ¹H NMR (400 MHz, CDCl₃) δ ppm 11.48 (br. s., 1H), 8.34(s, 1H), 3.53 (td, J=6.8, 13.7 Hz, 1H), 1.48 (d, J=7.1 Hz, 6H).

Step 5: 7-bromo-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(4.7 g, 26.2 mmol, Step 4) and LiOH.H₂O (3.14 g, 131 mmol) in CH₃OH (50mL) was added Br₂ (4.05 mL, 79 mmol) at 0° C. The resulting mixture wasstirred at 70° C. for 12 hours. The solvent was removed under reducedpressure to give a residue that was poured into H₂O and extracted withethyl acetate. The combined organic layer was dried over Na₂SO₄ andconcentrated in vacuum. The residue was purified by columnchromatography on silica gel (EtOAc/PE, 1:20-5) to give the titledcompound (1.3 g, yield 19%). ¹H NMR (400 MHz, CDCl₃) δ ppm 11.06 (br.s., 1H), 3.44 (td, J=7.0, 13.8 Hz, 1H), 1.41 (d, J=7.1 Hz, 6H).

Step 6:7-bromo-5-(4-chlorobenzyl)-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (600 mg,2.3 mmol, Step 5) in N,N-dimethylformamide (10 mL) was added K₂CO₃ (640mg, 4.6 mmol) and 1-chloro-4-(chloromethyl)benzene (650 mg, 4.1 mmol).After stirring at 50° C. for 2 hours, the mixture was diluted with waterand extracted with ethyl acetate. The combined organic phase was washedwith brine and concentrated in vacuum. The residue was purified bycolumn chromatography on silica gel (EtOAc/PE, 1:20-5) to give thetitled compound (560 mg, yield 59%). ¹H NMR (400 MHz, CDCl₃) δ ppm7.42-7.36 (m, 2H), 7.33-7.28 (m, 2H), 5.32 (s, 2H), 3.48 (td, J=6.7,13.9 Hz, 1H), 1.49-1.39 (m, 6H).

Step 7:N-{3-[5-(4-chlorobenzyl)-4-oxo-3-(propan-2-yl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(280 mg, 0.73 mmol, Step 6) in N,N-dimethylformamide (2 mL) and water(0.5 mL) was added (3-acetamidophenyl)boronic acid (132 mg, 0.735 mmol),K₂CO₃ (202 mg, 1.47 mmol) and tetrakis(triphenylphosphine)palladium(0)(30 mg, 0.037 mmol). After stirring at 80° C. overnight under nitrogen,the mixture was diluted with water and extracted with ethyl acetate. Theorganic phase was washed with brine and concentrated under reducedpressure to give a residue that was purified by preparative HPLC (methodC) to give the titled compound (45 mg, yield 14%). ¹H NMR (400 MHz,CDCl₃) δ ppm 8.11 (s, 1H), 7.82 (d, J=7.9 Hz, 1H), 7.70 (d, J=7.9 Hz,1H), 7.45-7.36 (m, 3H), 7.25 (d, J=8.4 Hz, 2H), 5.38 (s, 2H), 3.51 (td,J=7.0, 13.8 Hz, 1H), 2.17 (s, 3H), 1.41 (d, J=7.1 Hz, 6H); LCMS (methodB) (ESI+) m/z 436.1 (M+H)⁺, retention time 3.407 minutes.

Example 977-(2-amino-5-fluorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting4-fluoro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline formethyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by columnchromatography on silica gel eluted with 40% ethyl acetate/cyclohexane.The residue was triturated with a little ethyl acetate/diisopropyl ether(1:1), and the solid was dried overnight in a vacuum oven to give thetitled compound (19 mg, yield 29%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm 7.48(dd, J=10.2, 3.0 Hz, 1H), 7.44-7.37 (m, 4H), 7.10 (ddd, J=9.0, 8.1, 3.0Hz, 1H), 6.82 (dd, J=9.0, 5.1 Hz, 1H), 6.37 (q, J=7.0 Hz, 1H), 5.74 (s,2H), 2.62 (s, 3H), 1.74 (d, J=7.0 Hz, 3H); MS (ESI+) m/z 399.0 (M+H)⁺.

Example 985-[1-(4-chlorophenyl)ethyl]-7-[2-methoxy-5-(pyrrolidin-1-ylcarbonyl)phenyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

3-{5-[1-(4-Chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzamide(100 mg, 0.228 mmol, Example 59), potassium carbonate (44.6 mg, 0.322mmol), tetrabutylammonium hydrogensulfate (8.51 mg, 0.025 mmol) andpulverized sodium hydroxide (44.5 mg, 1.112 mmol) were combined in driedtoluene (4 mL). 1,4-Dibromobutane (59.0 mg, 0.033 mL, 0.273 mmol)dissolved in toluene was added dropwise to the stirred mixture. Theresultant mixture was heated to reflux or 2.5 hours. After cooling toroom temperature, the reaction mixture was partitioned between ethylacetate and water. The aqueous phase was extracted twice more with ethylacetate. The combined organic fractions were washed with brine, driedover MgSO₄, and concentrated under reduced pressure. The residue waspurified by flash chromatography using a Teledyne Isco CombiFlash® Rfapparatus with a 4 g RediSep® silica gel cartridge eluted with 8%methanol/dichloromethane. The residue was triturated with ethylacetate/diisopropyl ether to give a precipitate that collected and driedunder vacuum to give the titled compound (40 mg, yield 36%). ¹H NMR (600MHz, DMSO-d₆) δ ppm 7.78 (dd, J=8.6, 2.3 Hz, 1H), 7.60 (d, J=2.2 Hz,1H), 7.44-7.37 (m, 4H), 7.28 (d, J=8.7 Hz, 1H), 6.32 (q, J=7.0 Hz, 1H),3.85 (s, 3H), 3.46 (dt, J=8.6, 6.3 Hz, 4H), 2.59 (s, 3H), 1.85 (dp,J=25.5, 6.7 Hz, 3H), 1.73 (d, J=7.0 Hz, 3H); MS (ESI+) m/z 493.2 (M+H)⁺.

Example 995-(4-chlorobenzyl)-7-(3,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (3,4-dimethoxphenyl)boronic acid (61.5 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 73%.

¹H NMR (DMSO, 400 MHz):δ 7.66 (dd, J=8.38, 2.21 Hz, 1H), 7.52 (d, J=2.21Hz, 1H), 7.42 (s, 4H), 7.15 (d, J=8.82 Hz, 1H), 5.41 (s, 2H), 3.82 (d,J=3.09 Hz, 6H), 2.60 (s, 3H). m/z 411.8.

Example 1005-[1-(4-chlorophenyl)ethyl]-7-(2-hydroxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting (2-hydroxyphenyl)boronic acid for methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by columnchromatography on silica gel eluted with 30% ethyl acetate/cyclohexane.The residue was triturated with a little ethyl acetate/diisopropyl ether(1:1), and the solid was dried overnight in a vacuum oven to give thetitled compound (21 mg, yield 34%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm10.14 (s, 1H), 7.41 (s, 4H), 7.45-7.35 (m, 2H), 7.02-6.94 (m, 2H), 6.32(q, J=7.0 Hz, 1H), 2.59 (s, 3H), 1.74 (d, J=7.0 Hz, 3H); MS (ESI+) m/z382.1 (M+H)⁺.

Example 1017-(2-methoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2-methoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and4-(bromomethyl)-1-methoxy-2-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 15%.

¹H NMR (400 MHz, CD₃OD): δ 7.70-7.66 (m, 2H), 7.55-7.54 (m, 1H),7.44-7.42 (m, 1H), 7.19-7.16 (m, 2H), 7.13-7.10 (m, 1H), 5.42 (s, 2H),3.88 (s, 3H), 3.82 (s, 3H), 2.63 (s, 3H). m/z 445.3.

Example 1025-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added (2,5-dimethoxphenyl)boronic acid (61.5 mg, 0.338mmol), K₂CO₃ (0.097 g, 0.705 mmol) andtetrakis(triphenylphosphine)palladium(0) (0.033 g, 0.028 mmol). Theresulting mixture was stirred at 80° C. overnight under N₂. Aftercooling down to room temperature, the reaction mixture was concentratedunder reduced pressure to give a residue that was washed with a mixtureof CH₃OH and H₂O to give the titled compound. Yield 55%.

1H NMR (DMSO, 400 MHz):δ 7.34-7.45 (m, 4H), 7.09-7.20 (m, 2H), 6.98 (d,J=2.65 Hz, 1H), 5.37 (s, 2H), 3.74 (s, 3H), 3.71 (s, 3H), 2.57 (s, 3H).m/z 411.8.

Example 103N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1S)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamideStep 1:7-(5-amino-2-methoxyphenyl)-3-methyl-5-{(1S)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-3-methyl-5-{(1S)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 35, 100 mg, 0.249 mmol),4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (68.1mg, 0.274 mmol), sodium carbonate (79 mg, 0.746 mmol), and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (18.19 mg,0.025 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (3 mL) and water(0.3 mL) in a 5 mL sealed tube. The reaction mixture was irradiated at100° C. for 60 minutes in a microwave reactor. The reaction mixture wasthen concentrated, and the residue was purified by silica gel columnchromatography eluted with EtOAc/PE (1:4) to give the titled compound.

Step 2:N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1S)-4-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide

7-(5-Amino-2-methoxyphenyl)-3-methyl-5-{(1S)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(50 mg, 0.113 mmol, Step 1) and triethylamine (14.80 mg, 0.146 mmol)were combined in dichloromethane (10 mL). Acetyl chloride (9.71 mg,0.124 mmol) was added, and the reaction mixture was stirred at ambienttemperature for 1 hour. The reaction mixture was concentrated underreduced pressure, and the residue was purified by silica gel columnchromatography eluted with EtOAc/PE (4:1) to give the titled compound(10 mg, yield 15%). ¹H NMR (400 MHz, CD₃OD) δ ppm 1.89 (d, 3H), 2.15 (s,3H), 2.65 (s, 3H), 3.84 (s, 3H), 6.47 (q, 1H), 7.17 (d, 1H), 7.69 (m,5H), 7.76 (s, 1H); ¹⁹F NMR (376 MHz, CD₃OD) δ_(F) ppm −63.81 (s, 3F); MS(ESI+) m/z 509.3 (M+Na)⁻.

Example 104N-{3-[5-(4-chlorobenzyl)-4-oxo-3-phenyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamideStep 1: ethyl 4-oxo-2-phenyl-4,5-dihydrofuran-3-carboxylate

To an ice bath chilled solution of magnesiumethanolate (14.29 g, 125mmol) in toluene (30 mL) was added ethyl 3-oxo-3-phenylpropanoate (20 g,104 mmol) dropwise. The mixture was stirred at room temperature for 1hour. Anhydrous acetonitrile (30 mL) was added, and the mixture wascooled to -10° C. followed by the slowly addition of 2-chloroacetylchloride (11.75 g, 104 mmol). The mixture was then allowed to warm toroom temperature and left to stir for two hours. A dilute solution ofsulfuric acid (6 mL acid in 190 mL ice/water) was added, and the mixturewas extracted with tert-butylmethyl ether. The combined organicfractions were dried over Na₂SO₄ and filtered. The filtrate was thencooled to 0° C., and a solution of triethylamine (14.50 ml, 104 mmol) intert-butylmethyl ether (24 mL) was added. The reaction mixture wasstirred at room temperature overnight. The reaction mixture was dilutedwith water and extracted with dichloromethane. The organic phase wasdried over Na₂SO₄ and concentrated under reduced pressure to give aresidue that was purified by chromatography on silica gel and elutedwith EtOAc/PE to supply the titled compound (7.1 g, yield 29%). ¹H NMR(400 MHz, CDCl₃) δ ppm 7.89 (d, J=7.94 Hz, 2H), 7.55-7.65 (m, 1H),7.44-7.55 (m, 2H), 4.76 (s, 2H), 4.32 (q, J=7.06 Hz, 2H), 4.03-4.23 (m,1H), 1.30 (t, J=7.06 Hz, 3H).

Step 2: ethyl 5-(hydroxymethyl)-3-phenyl-1,2-oxazole-4-carboxylate

To a solution of ethyl 4-oxo-2-phenyl-4,5-dihydrofuran-3-carboxylate (7g, 30.1 mmol, Step 1) in anhydrous ethanol (100 mL) was added sodiumacetate (2.473 g, 30.1 mmol) and hydroxylamine hydrochloride (2.095 g,30.1 mmol). The mixture was heated to reflux for 3 hours. The volatileswere removed under reduced pressure to give a residue that was dilutedwith water and extracted with ethyl acetate. The organic phase waswashed with brine, dried over Na₂SO₄, and concentrated under reducedpressure. The resultant residue was purified by chromatography on silicagel and eluted with EtOAc/PE to give the titled compound (5.4 g, yield72%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.55-7.65 (m, 2H), 7.33-7.54 (m,3H), 4.96 (d, J=7.06 Hz, 2H), 4.26 (q, J=7.06 Hz, 2H), 3.90 (t, J=7.28Hz, 1H), 1.18 (t, J=7.06 Hz, 3H).

Step 3: ethyl 5-formyl-3-phenyl-1,2-oxazole-4-carboxylate

To a solution of ethyl5-(hydroxymethyl)-3-phenyl-1,2-oxazole-4-carboxylate (5.4 g, 21.84 mmol,Step 2) in anhydrous toluene (20 mL) was added MnO₂ (5.70 g, 65.5 mmol).The mixture was refluxed under N₂ overnight. The solids were removed byfiltration, and the filtrate was concentrated under reduced pressure.The resultant residue was purified by chromatography on silica geleluted with EtOAc/PE (1:30) to give the titled compound (3 g, yield56%). ¹H NMR (400 MHz, CDCl₃) δ ppm 10.30 (s, 1H), 7.61 (d, J=7.06 Hz,2H), 7.34-7.52 (m, 3H), 4.31 (q, J=7.20 Hz, 2H), 1.23 (t, J=7.28 Hz,3H).

Step 4: 3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To an ice-bath cooled solution of ethyl5-formyl-3-phenyl-1,2-oxazole-4-carboxylate (3 g, 12.23 mmol, Step 3) inethanol (30 mL) was added hydrazine hydrate (6.12 g, 122 mmol) dropwise.The mixture was stirred for 2 hours in an ice-bath. The precipitate wascollected by filtration and then dried to give the titled compound (2.1g, yield 81%). ¹⁻14 NMR (400 MHz, DMSO-d₆) δ ppm 8.78 (s, 1H), 8.33 (d,J=7.94 Hz, 2H), 7.53-7.62 (m, 3H).

Step 5: 7-bromo-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (2.1 g,7.19 mmol, Step 4) in a mixture solvent of ethyl acetate (5 mL) andmethanol (20 mL) was added lithium hydroxide hydrate (0.413 g, 9.85mmol) and bromine (1.574 g, 9.85 mmol) and the mixture was heated to 70°C. After stirring for 3 minutes, bromine (1.574 g, 9.85 mmol) was added,followed by the addition of lithium hydroxide hydrate (0.413 g, 9.85mmol). The mixture was heated to reflux overnight. The volatiles wereremoved under reduced pressure to give a residue that was diluted withwater and extracted with ethyl acetate. The organic phase was dried overNa₂SO₄ and concentrated under reduced pressure to give the titledcompound (2.3 g, yield 80%) which was used for next step without furtherpurification. ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.24-8.47 (m, 2H),7.46-7.64 (m, 3H).

Step 6:7-bromo-5-(4-chlorobenzyl)-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 7-bromo-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(180 mg, 0.616 mmol, Step 5) in N,N-dimethylformamide (4 mL) was addedpotassium carbonate (85 mg, 0.616 mmol). Then1-chloro-4-(chloromethyl)benzene (99 mg, 0.616 mmol) was added in oneportion. The resulting mixture was stirred at room temperature for 4hours. The reaction mixture was diluted with water and extracted withethyl acetate. The organic fraction was washed with brine andconcentrated under reduced pressure. The residue was washed withmethanol and dried to give the titled compound (220 mg, yield 86%). ¹HNMR (400 MHz, DMSO-d₆) δ ppm 8.21 (d, J=6.62 Hz, 2H), 7.50-7.66 (m, 3H),7.29-7.46 (m, 4H), 5.36 (s, 2H).

Step 7:N-{3-[5-(4-chlorobenzyl)-4-oxo-3-phenyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(130 mg, 0.312 mmol, Step 6) in 1,2-dimethoxyethane (4 mL) and water (1mL) was added (3-acetamidophenyl)boronic acid (67.0 mg, 0.374 mmol),K₂CO₃ (108 mg, 0.780 mmol) and tetrakis(triphenylphosphine)palladium(0)(36 mg, 0.031 mmol). After stirring at 80° C. overnight, the mixture wasdiluted with water and extracted with ethyl acetate. The organic phasewas washed with brine and concentrated under reduced pressure. Theresidue was washed with methanol and dried to give the titled compound.¹H NMR (400 MHz, DMSO-d₆) δ ppm 10.22 (s, 1H), 8.36 (s, 1H), 8.26 (d,J=7.94 Hz, 2H), 7.71-7.85 (m, 2H), 7.56-7.63 (m, 3H), 7.48-7.56 (m, 1H),7.38-7.46 (m, 4H), 5.47 (s, 2H) 2.08 (s, 3H); LCMS (method B) (ESI+) m/z470.9 (M+H)⁺, retention time 3.456 minutes.

Example 105N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamideStep 1:7-(5-amino-2-methoxyphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 35, 100 mg, 0.249 mmol),4-methoxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (68.1mg, 0.274 mmol), sodium carbonate (79 mg, 0.746 mmol), and [1,1¹-bis(diphenylphosphino)ferrocene] dichloropalladium(II) (18.19 mg,0.025 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (3 mL) and water(0.3 mL) in a 5 mL sealed tube. The reaction mixture was irradiated at100° C. for 60 minutes in a microwave reactor. The reaction mixture wasthen concentrated, and the residue was purified by silica gel columnchromatography eluted with EtOAc/PE (1:3) to give the titled compound.

Step 2:N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide

7-(5-Amino-2-methoxyphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(50 mg, 0.113 mmol, Step 1) and triethylamine (22.77 mg, 0.225 mmol)were combined in dichloromethane (10 mL). Acetyl chloride (9.71 mg,0.124 mmol) was added, and the reaction mixture was stirred at ambienttemperature for 1 hour. The reaction mixture was concentrated underreduced pressure, and the residue was purified by silica gel columnchromatography eluted with EtOAc/PE (4:1) to give the titled compound(17 mg, yield 25%). ¹H NMR (400 MHz, CD₃OD) δ ppm 1.89 (d, 3H), 2.15 (s,3H), 2.65 (s, 3H), 3.84 (s, 3H), 6.47 (q, 1H), 7.17 (d, 1H), 7.69 (m,5H), 7.76 (s, 1H); MS (ESI+) m/z 487.2 (M+H)⁺.

Example 1063-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamide

The titled compound was prepared using the procedure described inExample 4 substituting (3-carbamoylphenyl)boronic acid (26 mg, 0.16mmol) for (2,6-difluoropyridin-4-yl)boronic acid. Purification wasachieved by preparative liquid chromatography (Method C, 0.5-8.5 minuteslinear gradient 40-70% A). ¹H NMR (400 MHz,DMSO-d₆/D₂O, Temperature=90°C.) δ ppm 8.51 (t, J=1.8 Hz, 1H), 8.21-8.15 (m, 1H), 8.02-7.97 (m, 1H),7.67 (t, J=7.9 Hz, 1H), 7.47-7.42 (m, 2H), 7.40-7.35 (m, 2H), 6.34 (q,J=7.0 Hz, 1H), 2.62 (s, 3H), 1.84 (d, J=7.0 Hz, 3H); MS (APCI+) m/z 409(M+H)⁻.

Example 107N-(4-methyl-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamideStep 1:7-(5-amino-2-methylphenyl)-3-methyl-5-[4-(trifluoromethyl)-benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 64, 120 mg, 0.309 mmol),4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (22.62mg, 0.031 mmol), sodium carbonate (82 mg, 0.773 mmol), and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (226 mg,0.309 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (2 mL) and water(0.2 mL) in a 5-mL sealed tube. The reaction mixture was irradiated in amicrowave reactor for 45 minutes at 100° C. The reaction mixture wasthen concentrated under reduced pressure, and the residue was purifiedby silica gel column chromatography eluted with EtOAc/PE (1:4) to givethe titled compound.

Step 2:N-(4-methyl-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide

7-(5-Amino-2-methylphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(60 mg, 0.145 mmol, Step 1) and triethylamine (14.65 mg, 0.145 mmol)were combined in dichloromethane (5 mL). Then acetyl chloride (11.73 mg,0.145 mmol) was added, and the resultant reaction mixture was stirred atambient temperature for 1 hour. The mixture was concentrated underreduced pressure, and the residue was purified by reverse phase (C18)column chromatography eluted with methanol/water (9:1) to give thetitled compound (30 mg, yield 46%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.04(s, 3H), 2.17 (s, 3H), 2.61 (s, 3H), 5.51 (s, 2H), 7.31 (d, 1H), 7.57(m, 3H), 7.72 (d, 2H), 7.82 (s, 1H), 10.09 (brs, 1H); MS (ESI−) m/z−454.9 (M−H)⁻.

Example 1083,7-dimethyl-5-(3-methylbutyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 1-bromo-3-methylbutane for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 50-80% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 4.16-4.08 (m,2H), 2.57 (s, 3H), 2.50 (s, 3H), 1.63-1.55 (m, 3H), 0.92 (d, J=6.1 Hz,6H); MS (APCI⁺) m/z236.1 (M+H)⁺.

Example 1095-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(pyridin-3-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 4 substituting pyridin-3-ylboronic acid (20 mg, 0.16 mmol) for(2,6-difluoropyridin-4-yl)boronic acid. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 35-65% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O, Temperature=90° C.) δppm 9.18 (d, J=2.2 Hz, 1H), 8.71 (dd, J=4.9, 1.6 Hz, 1H), 8.39 (dt,J=8.0, 2.0 Hz, 1H), 7.68-7.57 (m, 1H), 7.50-7.32 (m, 4H), 6.34 (q, J=7.0Hz, 1H), 2.62 (s, 3H), 1.83 (d, J=7.0 Hz, 3H); MS (APCI⁺) m/z 367(M+H)⁺.

Example 110N-{3-[3-methyl-4-oxo-5-(pyridin-4-ylmethyl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

The titled compound was prepared using the procedures described forExample 5 substituting (3-acetamidophenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1. Yield 59%.

¹H NMR (400 MHz, CD₃OD): δ 8.76 (s, 2H), 8.48 (s, 1H), 7.96-7.94 (d,J=6.4 Hz, 2H), 7.88-7.86 (d, J=8.0 Hz, 1H), 7.64-7.62 (d, J=8.0 Hz, 1H),7.50-7.46 (t, J=8.0 Hz, 1H), 5.76 (s, 2H), 2.67 (s, 3H), 2.16 (s, 3H).m/z 376.2.

Example 1113-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide

Under argon,7-bromo-5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl[1,2]-oxazolo[4,5-d]pyridazin-4(5H)-one(Example 82, 300 mg, 0.814 mmol) was suspended in toluene and ethanol(12 mL, 1:1). 2 M Aqueous sodium bicarbonate (0.610 mL, 1.221 mmol) and4-methoxy-N-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzamide (261 mg, 0.895 mmol,Example 119-Step 1) were added followed bytetrakis(triphenylphosphine)palladium(0) (94 mg, 0.081 mmol). Thereaction mixture was heated with stirring in a Biotage® microwavereactor at 130° C. for 30 minutes. The reaction mixture was thenpartitioned between water and ethyl acetate. The organic fraction waswashed with brine, dried over MgSO₄ and then concentrated under reducedpressure. The residue was purified by flash chromatography on a TeledyneIsco CombiFlash® Rf apparatus using a silica gel cartridge (4 g) elutedwith 3-5% methanol/dichloromethane. A second flash chromatography on aTeledyne Isco CombiFlash® Rf apparatus using a silica gel cartridge (4g, 15 μm) eluted with 50% ethyl acetate/heptane was performed. Theresidue was stirred with diisopropyl ether and collected by vacuumfiltration. The precipitate was dissolved in ethyl acetate andconcentrated. The residue was stirred again with diisopropyl ether, andthe precipitate was collected by vacuum filtration. The precipitate wasdried in a vacuum oven overnight to give the titled compound (117 mg,yield 32%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm 8.46 (q, J=4.5 Hz, 1H), 8.05(dd, J=8.7, 2.3 Hz, 1H), 7.95 (d, J=2.3 Hz, 1H), 7.41 (s, 4H), 7.32 (d,J=8.8 Hz, 1H), 6.33 (q, J=7.0 Hz, 1H), 3.85 (s, 3H), 3.32 (s, 1H), 2.79(d, J=4.5 Hz, 3H), 2.59 (s, 3H), 1.75 (d, J=7.1 Hz, 3H), 1.04 (d, J=6.1Hz, 1H).

Example 112N-[6-fluoro-2-methyl-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)-phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide

7-Bromo-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo-[4,5-d]pyridazin-4(5H)-one(Example 35, 100 mg, 0.249 mmol),N-(6-fluoro-2-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetamide(80 mg, 0.274 mmol), sodium carbonate (79 mg, 0.746 mmol), and[1,1¹-bis(diphenyl-phosphino)ferrocene]dichloropalladium(II) (18.19 mg,0.025 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (5 mL) and water(0.5 mL) under a nitrogen atmosphere. The reaction mixture was stirredat 100° C. for 3 hours. The reaction mixture was then concentrated, andthe residue was purified by silica gel column chromatography eluted withEtOAc/PE (1:3) to give the titled compound (25 mg, yield 17%).

¹H NMR (400 MHz, CD₃OD) δ ppm 1.87 (d, 3H), 2.15 (s, 3H), 2.21 (s, 3H),2.68 (s, 3H), 6.52 (q, 1H), 7.23 (t, 1H), 7.54 (m, 1H), 7.64 (m, 4H); MS(ESI+) m/z 489.2 (M+H)⁺.

Example 113 5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(pyrimidin-5-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting pyrimidin-5-ylboronic acid for methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by columnchromatography on silica gel eluted with 30% ethyl acetate/cyclohexane.The residue was triturated with a little ethyl acetate/diisopropyl ether(1:1), and the solid was collected by vacuum filtration. The filtratewas concentrated, and the residue was treated overnight with ethylacetate/diisopropyl ether (1:9). The combined solids were driedovernight in a vacuum oven to give the titled compound. ¹H NMR (600 MHz,DMSO-d₆) δ ppm 9.40 (s, 2H), 9.36 (s, 1H), 7.53-7.48 (m, 2H), 7.44-7.37(m, 2H), 6.34 (q, J=7.0 Hz, 1H), 3.34 (s, OH), 2.62 (s, 3H), 1.82 (d,J=7.0 Hz, 3H); MS (ESI+) m/z 368.2 (M+H)⁺.

Example 1145-[1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-oneStep 1: 1-(1-bromoethyl)-4-chlorobenzene

To a solution of 1-(4-chlorophenyl)ethanol (3.132 g, 20.00 mmol) inanhydrous CH₂Cl₂ (30 mL) was added pyridine (4.84 mL, 60.0 mmol), andthe solution chilled to −20° C., followed by the slow addition of 1.0 MPBr₃ (20.00 mL, 20.00 mmol). The reaction was stirred at ambienttemperature for 36 hours. The reaction was quenched by the addition of150 mL of ice, and the mixture was stirred for 30 minutes. The mixturewas then diluted with water (200 mL) containing citric acid (2 g) andthen extracted four times with diethyl ether. The combined organicextracts were washed with brine, dried over MgSO₄, filtered andconcentrated to give the titled compound (2.635 g, 60% yield). ¹H NMR(300 MHz, CDCl₃) δ ppm 7.48-7.34 (m, 4H), 5.24 (q, J=6.9, 6.9, 6.9 Hz,1H), 2.09 (dd, J=6.9, 0.4 Hz, 3H).

Step 2:5-[1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

Anhydrous potassium carbonate (1.657 g, 11.99 mmol) was added to asolution of 3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (1.32 g,7.99 mmol) in N,N-dimethylformamide (50 ml) followed by the dropwiseaddition of a solution of 1-(1-bromoethyl)-4-chlorobenzene (1.930 g,8.79 mmol, Step 1) in N,N-dimethylformamide (1.5 mL). The reactionmixture was heated at 56° C. for 2 hours, then cooled to ambienttemperature and poured into an aqueous brine/ammonium chloride solution.The mixture was extracted with ethyl acetate (3×). The combined organicextracts were washed with brine, dried (MgSO₄), filtered andconcentrated under reduced pressure. The residue was purified by silicagel chromatography, eluting with a gradient of 10-40% ethyl acetate inheptane to give 2.43 g (100%) of the titled compound. ¹H NMR (300 MHz,CDCl₃) δ ppm 7.43-7.37 (m, 2H), 7.30 (d, J=9.8 Hz, 2H), 6.36 (q, J=7.1,7.1, 7.1 Hz, 1H), 2.68 (s, 3H), 2.58 (s, 3H), 1.79 (d, J=7.1 Hz, 3H); MS(DCI/NH₃) m/z 304 (M+H)⁺, 321 (M+NH₄)⁺.

Example 1155-[1-(4-chlorophenyl)ethyl]-7-(1-ethyl-1H-pyrazol-5-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting (1-ethyl-1H-pyrazol-5-yl)boronic acid formethyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography using a Teledyne Isco CombiFlash® Rf apparatus with a 4 gsilica gel cartridge eluted with 35% ethyl acetate/cyclohexane. Theresidue was dried under vacuum to give the titled compound. ¹H NMR (600MHz, DMSO-d₆) δ ppm 7.66 (d, J=2.0 Hz, 6H), 7.40 (q, J=8.8 Hz, 34H),7.00 (d, J=2.0 Hz, 6H), 6.39 (q, J=7.0 Hz, 9H), 4.33 (ddq, J=34.6, 13.6,7.0 Hz, 22H), 1.77 (d, J=7.0 Hz, 30H), 1.26-1.17 (m, 37H).

Example 1165-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(1H-pyrrolo[3,2-b]pyridin-6-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was obtained using the reaction conditions describedfor Example 6 substituting6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrrolo[3,2-b]pyridinefor methyl(4-chloro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)carbamate.The reaction mixture was partitioned between ethyl acetate and water.The organic fraction was washed with brine, dried over MgSO₄, andconcentrated under reduced pressure. The residue was purified by flashchromatography using a Teledyne Isco CombiFlash® Rf apparatus with a 4 gsilica gel cartridge eluted with ethyl acetate/cyclohexane. The residuewas triturated with 60% ethyl acetate/diisopropyl ether (1:1). Thecollected solid was dried under vacuum to give the titled compound (13mg, yield 20%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm 11.61 (s, 1H), 9.00 (d,J=2.0 Hz, 1H), 8.44 (dd, J=2.0, 0.9 Hz, 1H), 7.84 (dd, J=3.2, 1.5 Hz,1H), 7.51-7.45 (m, 2H), 7.46-7.39 (m, 2H), 6.67 (d, J=3.1 Hz, 1H), 6.37(q, J=7.0 Hz, 1H), 2.63 (s, 3H), 1.84 (d, J=7.0 Hz, 3H), 1.04 (d, J=6.1Hz, 1H).

Example 117N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide

The enantiomers ofN-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide(0.4 g, 0.883 mmol, Example 39) were separated by chiral super criticalchromatograph (method B) to give the titled compound (0.09 g, yield 23%)andN-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide(0.08 g, yield 20%, Example 40). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.63 (dd,J=2.4, 9.0 Hz, 1H), 7.56 (d, J=2.6 Hz, 1H), 7.44 (d, J=8.4 Hz, 2H),7.35-7.23 (m, 3H), 7.01 (d, J=8.8 Hz, 1H), 6.39 (q, J=7.1 Hz, 1H), 3.82(s, 3H), 2.67 (s, 3H), 2.19 (s, 3H), 1.82 (d, J=7.1 Hz, 3H); LCMS(method C) (ESI+) m/z 453.1 (M+H)⁺, retention time 3.240 minutes.

Example 1187-(2-methoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2-methoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)-boronic acid in Step 1 and1-(bromomethyl)-4-(trifluoromethyl)benzene for 4-(bromomethyl)pyridinein Step 2. Yield 22%.

¹H NMR (400 MHz, CD₃OD): δ 7.66-7.65 (m, 2H), 7.61-7.59 (m, 2H),7.58-7.52 (m, 1H), 7.46-7.43 (m, 1H), 7.19-7.17 (m, 1H), 7.12-7.10 (m,1H), 5.53 (s, 2H), 3.83 (s, 3H), 2.62 (s, 3H). m/z 415.4.

Example 1193-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamideStep 1:4-methoxy-N-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzamide

3-Bromo-4-methoxy-N-methylbenzamide (1.00 g, 4.10 mmol),4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-bi(1,3,2-dioxaborolane) 1.457 g(5.74 mmol), potassium carbonate (1.005 g, 10.24 mmol, and[1,1′-bis(diphenylphosphino)ferro-cene]dichloropalladium(II)dichloromethane complex (167 mg, 0.205 mmol) were combined in dioxane(10 mL) and heated to 90° C. for 7 hours. The reaction mixture was thenconcentrated under reduced pressure. The residue was combined with ethylacetate (25 mL), and remaining residue was removed by filtration. Ethylacetate was distilled off, and the residue was purified by flashchromatography on a Teledyne Isco CombiFlash® apparatus using a RediSep®silica gel cartridge (40 g) eluted with 10% methanol/dichloromethane.Impurities remained, and a second flash chromatography on a TeledyneIsco CombiFlash® apparatus using a RediSep® silica gel cartridge (40 g)eluted with ethyl acetate was performed to give the titled compound.

Step 2:3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide

7-Bromo-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(80 mg, 0.217 mmol, Example 39-Step 5) in ethanol/toluene (1:1, 2 mL)was combined with 2 M aqueous sodium carbonate (0.163 mL, 0.326 mmol)and4-methoxy-N-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzamide(63.2 mg, 0.217 mmol, Step 1). Thentetrakis(triphenylphosphine)palladium(0) (25.08 mg, 0.022 mmol) wasadded, and the mixture was heated in a CEM microwave reactor for 30minutes at 130° C. under an argon atmosphere. The reaction mixture waspartitioned between water and dichloromethane. The organic fraction wasthen washed with brine, dried over MgSO₄, and concentrated under reducedpressure. The residue was purified by flash chromatography on a TeledyneIsco CombiFlash® Rf apparatus using a silica gel cartridge (4 g) elutedwith 4% methanol/dichloromethane. Impurities remained, and a secondflash chromatography on a Teledyne Isco CombiFlash® Rf apparatus using asilica gel cartridge (4 g) eluted with ethyl acetate was performed. Thetitled compound was obtained after drying overnight in a vacuum oven (22mg, yield 22%). ¹H NMR (600 MHz, DMSO-d₆) δ ppm 8.46 (q, J=4.5 Hz, 1H),8.05 (dd, J=8.7, 2.3 Hz, 1H), 7.95 (d, J=2.3 Hz, 1H), 7.41 (s, 4H), 7.32(d, J=8.8 Hz, 1H), 6.33 (q, J=7.0 Hz, 1H), 3.85 (s, 3H), 2.79 (d, J=4.5Hz, 3H), 2.59 (s, 3H), 1.75 (d, J=7.1 Hz, 3H); MS (ESI+) m/z 453.2(M+H)⁺.

Example 1205-(4-chlorobenzyl)-3-methyl-7-(pyridin-3-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxyethane (4 mL) andwater (1 mL) was added pyridin-3-ylboronic acid (41.5 mg, 0.338 mmol),K₂CO₃ (0.097 g, 0.705 mmol) and tetrakis(triphenylphosphine)palladium(0)(0.033 g, 0.028 mmol). The resulting mixture was stirred at 80° C.overnight under N₂. After cooling down to room temperature, the reactionmixture was concentrated under reduced pressure to give a residue thatwas washed with a mixture of CH₃OH and H₂O to give the titled compound.Yield 48%.

¹H NMR (DMSO, 400 MHz):δ 9.18 (d, J=1.76 Hz, 1H), 8.69-8.75 (m, 1H),8.38 (d, J=7.94 Hz, 1H), 7.63 (dd, J=7.94, 4.85 Hz, 1H), 7.37-7.46 (m,4H), 5.44 (s, 2H), 2.61 (s, 3H). m/z 352.8.

Example 1213,7-dimethyl-5-[3-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 1-(bromomethyl)-3-(trifluoromethyl)benzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 60-100% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.70-7.65 (m,2H), 7.58 (dd, J=5.0, 1.8 Hz, 2H), 5.40 (s, 2H), 2.57 (s, 3H), 2.51 (s,3H); MS (APCI⁺) m/z324.1 (M+H)⁺.

Example 1225-(4-chlorobenzyl)-3-methyl-7-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of7-bromo-5-(4-chlorobenzyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.1 g, 0.282 mmol, Example 2-Step 6) in 1,2-dimethoxy-ethane (4 mL) andwater (1 mL) was added phenylboronic acid (41.2 mg, 0.338 mmol), K₂CO₃(0.097 g, 0.705 mmol) and tetrakis(triphenylphosphine)palladium(0)(0.033 g, 0.028 mmol). The resulting mixture was stirred at 80° C.overnight under N₂. After cooling down to room temperature, the reactionmixture was concentrated under reduced pressure to give a residue thatwas washed with a mixture of CH₃OH and H₂O to give the titled compound.Yield 47%.

¹H NMR (CDCl₃, 400 MHz):δ 8.14 (d, J=6.62 Hz, 2H), 7.38-7.60 (m, 5H),7.32 (d, J=8.38 Hz, 2H), 5.44 (s, 2H), 2.72 (s, 3H). m/z 351.8.

Example 1235-(2,4-difluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one1-(bromomethyl)-2,4-difluorobenzene

The titled compound was prepared using the procedure described inExample 20 substituting 1-(bromomethyl)-2,4-difluorobenzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 45-75% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.35 (td, J=8.7,6.6 Hz, 1H), 7.23 (ddd, J=10.5, 9.4, 2.6 Hz, 1H), 7.08-7.01 (m, 1H),5.32 (s, 2H), 2.57 (s, 3H), 2.49 (s, 3H); MS (APCI⁺) m/z 292.0 (M+H)⁺.

Example 1243,7-dimethyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 20 substituting 1-(bromomethyl)-4-(trifluoromethyl)benzene for1-(bromomethyl)-2-fluorobenzene. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 60-100% A). ¹H NMR (400 MHz, DMSO-d₆/D₂O) δ ppm 7.71 (d, J=8.2Hz, 2H), 7.51 (d, J=8.0 Hz, 2H), 5.40 (s, 2H), 2.57 (s, 3H), 2.51 (s,3H); MS (APCI⁺) m/z 324.0 (M+H)⁺.

Example 1257-(2,5-dimethoxyphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

7-Bromo-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(Example 35, 100 mg, 0.249 mmol),2-(2,5-dimethoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (72.2mg, 0.274 mmol), sodium carbonate (79 mg, 0.746 mmol), and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (18.19 mg,0.025 mmol, PdCl₂(dppf)) were combined with 1,4-dioxane (5 mL) and water(0.5 mL) under a nitrogen atmosphere. The reaction mixture was stirredat 100° C. for 3 hours. The reaction mixture was then concentrated underreduced pressure, and the residue was purified by silica gel columnchromatography eluted with EtOAc/PE (1:3) to give the titled compound(10 mg, yield 9%).

¹H NMR (400 MHz, CD₃OD) δ ppm 1.88 (d, 3H), 2.65 (s, 3H), 3.78 (s, 6H),6.48 (q, 1H), 6.96 (s, 1H), 7.12 (m, 2H), 7.66 (m, 4H); ¹⁹F NMR (282MHz, CDCl₃) δ_(F) ppm −63.23 (s, 3F); MS (ESI+) m/z 460.2 (M+H)⁺.

Example 1267-(3-aminophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedure described inExample 4 substituting (3-aminophenyl)boronic acid (22 mg, 0.16 mmol)for (2,6-difluoropyridin-4-yl)boronic acid. Purification was achieved bypreparative liquid chromatography (Method C, 0.5-8.5 minutes lineargradient 35-65% A). (12 mg, yield 17%).

¹H NMR (400 MHz,DMSO-d₆/D₂O, Temperature=90° C.) δ ppm 7.47-7.36 (m,4H), 7.34-7.30 (m, 1H), 7.25-7.19 (m, 2H), 6.80-6.74, (m, 1H), 6.38-6.27(m, 1H), 2.61 (s, 3H), 1.81 (d, J=7.0 Hz, 3H); MS (APCI+) m/z 381(M+H)⁺.

Example 1277-(2,4-dimethoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting 1-(bromomethyl)-4-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 9%.

¹H NMR (400 MHz, CD₃OD): δ7.66-7.64 (d, J=8.4 Hz, 2H), 7.60-7.58 (d,J=8.4 Hz, 2H), 7.38-7.36 (d, J=8.4 Hz, 1H), 6.67-6.65 (m,2H), 5.52 (s,2H), 3.87 (s, 3H), 3.81 (s, 3H), 2.63 (s, 3H). m/z 446.0.

Example 1285-[(1R)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)-[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

5-[1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)-[1,2]oxazolo[4,5-d]pyridazin-4(5H)-onewas synthesized in analogy to example 1. The enantiomers were separatedby supercritical fluid chromatography to give the titled compound. Themobile phase was comprised of supercritical CO₂ supplied by a bulk tankof 99.5% bone-dry non-certified CO₂ pressurized to 1200 psi (82.7 bar)with a modifier of methanol (0.1 N NH₄OH) at a flow rate of 70 g/minute.UV detection was set to collect at a wavelength of 220 nm, the columnwas heated to 35° C., and the backpressure regulator was set to maintain100 bar. The sample was dissolved in methanol at a concentration ofabout 50 mg/mL, and the injection volume was 1 mL. The mobile phase washeld isocratically at 40% methanol (0.1 N NH₄OH):CO2. The instrument wasfitted with a Chiralpak® AS-H 5 μm, 30 mm×250 mm column. ¹H NMR (400MHz, DMSO-d₆) δ ppm 7.39 (s, 3H), 7.17-7.08 (m, 2H), 6.92 (d, J=2.6 Hz,1H), 6.30 (q, J=6.9 Hz, 1H), 3.71 (d, J=7.1 Hz, 6H), 2.46-2.39 (m, 1H),1.71 (d, J=7.1 Hz, 3H), 1.14 (d, J=7.5 Hz, 4H).

Example 129N-{3-[5-(4-chlorobenzyl)-3-ethyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamideStep 1: ethyl 2-ethyl-4-oxo-4,5-dihydrofuran-3-carboxylate

To an ice bath cooled solution of magnesiumethanolate (17.58 g, 154mmol) in toluene (100 mL) was added ethyl 3-oxopentanoate (20 g, 154mmol) dropwise. The mixture was stirred at room temperature for 1 hour.Anhydrous acetonitrile (100 mL) was added to the mixture at −10° C.followed by the slow addition of 2-chloroacetyl chloride (20.83 g, 184mmol). The mixture was allowed to warm to room temperature and left tostir for 2 hours. A dilute solution of sulfuric acid (8 mL acid in 280mL ice/water) was added, followed by extraction with tert-butylmethylether. The combined organic fractions were dried over Na₂SO₄ andfiltered. The filtrate was cooled to 0° C. A solution of triethylamine(107 mL, 768 mmol) in tert-butyl methyl ether (100 mL) was added. Thereaction mixture was left to stir at room temperature overnight. Themixture was diluted with water, and extracted with dichloromethane. Theorganic phase was concentrated under reduced pressure to give a residuethat was purified by column chromatography on silica gel and eluted withEtOAc/PE to give the titled compound (15 g, yield 57.4%). ¹H NMR (400MHz, CDCl₃) δ ppm 4.53 (s, 2H), 4.25-4.18 (m, 2H), 2.95 (q, J=7.5 Hz,2H), 1.28-1.17 (m, 6H).

Step 2: ethyl 3-ethyl-5-(hydroxymethyl)-1,2-oxazole-4-carboxylate

To a solution of ethyl 2-ethyl-4-oxo-4,5-dihydrofuran-3-carboxylate (8.0g, 40 mmol, Step 1) in anhydrous ethanol (50 mL) was added sodiumacetate (3.6 g, 40 mmol) and hydroxylamine (2.8 g, 40 mmol). The mixturewas heated to reflux for 1 hour and then concentrated. The residue wasdiluted with water and extracted with ethyl acetate. The organic phasewas washed with brine, dried over Na₂SO₄, and concentrated under reducedpressure. The residue which was purified by column chromatography onsilica gel and eluted with EtOAc/PE to give the titled compound (6.1 g,yield 94%). ¹H NMR (400 MHz, CDCl₃) δ ppm 4.85 (s, 2H), 4.32 (q, J=7.1Hz, 2H), 4.11-4.03 (m, 1H), 2.88-2.80 (m, 2H), 1.38-1.32 (m, 3H), 1.25(t, J=7.5 Hz, 3H).

Step 3: ethyl 3-ethyl-5-formyl-1,2-oxazole-4-carboxylate

To a solution of ethyl3-ethyl-5-(hydroxymethyl)-1,2-oxazole-4-carboxylate (6.0 g, 30 mmol,step 2) in anhydrous toluene (200 mL) was added manganese(IV) oxide (7.9g, 90 mmol). The mixture was heated to reflux for 6 hours. The manganesesalts were removed by filtration, and the filtrate was concentratedunder reduced pressure. The residue was purified by columnchromatography on silica gel and eluted with EtOAc/PE to give the titledcompound (3.3 g, yield 56%). ¹H NMR (400 MHz, CDCl₃) δ ppm 10.33 (s,1H), 4.45-4.30 (m, 2H), 3.55 (s, 1H), 3.02-2.82 (m, 2H), 1.48-1.19 (m,6H).

Step 4: 3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of ethyl 3-ethyl-5-formyl-1,2-oxazole-4-carboxylate (3.02g, 15.3 mmol, Step 3) in ethanol (60 mL) chilled in an ice-bath wasadded hydrazine hydrate (3.72 mL, 119 mmol) dropwise. The resultingmixture was stirred for 2 hours. The mixture was filtered throughdiatomaceous earth, and the filtrate was diluted with ethyl acetate (200mL) and water (50 mL). The solid was collected by filtration and driedto give the titled compound (2.1 g, yield 83%). ¹H NMR (400 MHz,methanol-d₄) δ ppm 11.80 (br. s., 1H), 8.30-8.27 (m, 1H), 3.09-3.00 (m,2H), 1.43-1.34 (m, 3H).

Step 5: 7-bromo-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one (2.0 g,12 mmol, Step 4) in methanol (120 mL) chilled in an ice-water bath wasadded lithium hydroxide hydrate (1.43 g, 60 mmol) and Br₂ (0.012 g, 72mmol) dropwise. The mixture was heated to reflux overnight. The mixturewas diluted with water and extracted with ethyl acetate. The organicphase was washed with brine, dried over Na₂SO₄, and concentrated underreduced pressure. The residue was purified by column chromatography onsilica gel and eluted with EtOAc/PE to give the titled compound (1.65 g,yield 70%). ¹H NMR (400 MHz, CDCl₃) δ ppm 3.03 (q, J=7.6 Hz, 2H), 1.39(t, J=7.7 Hz, 3H).

Step 6:7-bromo-5-(4-chlorobenzyl)-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

To a solution of 7-bromo-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(0.20 g, 0.83 mmol, Step 5) in N,N-dimethylformamide (3 mL) was addedK₂CO₃ (0.57 g, 4.15 mmol) at room temperature.1-Chloro-4-(chloromethyl)benzene (0.17 g, 1.07 mmol) was added in oneportion. The mixture was heated to 80° C. for 2 hours. The reactionmixture was concentrated, diluted with water (20 mL), and extracted withethyl acetate (50 mL×3). The combined organic layers were dried overNa₂SO₄, filtered and concentrated in vacuum to give the titled compound(0.45 g, yield 99%). ¹H NMR (400 MHz, CDCl₃) δ ppm 7.42-7.38 (m, 2H),7.34-7.29 (m, 2H), 5.32 (s, 2H), 3.09-3.02 (m, 2H), 1.40 (t, J=7.5 Hz,3H).

Step 7:N-{3-[5-(4-chlorobenzyl)-3-ethyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide

To a solution of7-bromo-5-(4-chlorobenzyl)-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one(216 mg, 0.586 mmol, Step 6) in 1,4-dioxane (5 mL) and water (2 mL) wasadded (3-acetamidophenyl)boronic acid (105 mg, 0.58 mmol), K₂CO₃ (62.1mg, 0.58 mmol) and tetrakis(triphenylphosphine)palladium(0) (67.7 mg,0.059 mmol) at room temperature under nitrogen. After stirring at 80° C.overnight, the mixture was diluted with water, and extracted with ethylacetate (20 mL×3). The organic phase was washed with brine andconcentrated in vacuum. The residue was purified by preparative HPLC(method B) to give the titled compound (82.5 mg, yield 33%). ¹H NMR (400MHz, CDCl₃) δ ppm 8.11 (s, 1H), 7.82 (d, J=7.9 Hz, 1H), 7.71 (d, J=7.9Hz, 1H), 7.44-7.41 (m, 1H), 7.40-7.38 (m, 1H), 7.38-7.36 (m, 1H), 7.31(br. s., 1H), 7.25-7.22 (m, 1H), 7.19 (s, 1H), 5.37 (s, 2H), 3.05 (q,J=7.6 Hz, 2H), 2.17 (s, 3H), 1.37 (t, J=7.5 Hz, 3H); LCMS (method B)(ESI+) m/z 422.9 (M+H)⁺, retention time 3.138 minutes

Example 1307-(2,5-dimethoxyphenyl)-5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one

The titled compound was prepared using the procedures described forExample 5 substituting (2,5-dimethoxyphenyl)boronic acid for(2,4-dimethoxyphenyl)boronic acid in Step 1 and2-(bromomethyl)-1-fluoro-4-(trifluoromethyl)benzene for4-(bromomethyl)pyridine in Step 2. Yield 46%.

¹H NMR (400 MHz, CD₃OD): δ7.77-7.68 (m, 2H), 7.36-7.31 (m, 1H), 7.09(s,2H), 6.94 (s, 2H), 5.57 (s, 2H), 3.77 (s, 3H), 3.76 (s, 3H), 2.63 (s,3H). m/z 464.0.

Example 1313-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-N-ethyl-4-methoxybenzamide

Sodium hydride (3.28 mg, 0.137 mmol, 5.47 mg of 60% dispersion in oil)was added to a solution of3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzamide(50 mg, 0.114 mmol, Example 59) dissolved in N,N-dimethylformamide (1mL). After 30 minutes, iodoethane (10.99 μL, 21.32 mg, 0.137 mmol) wasadded, and the reaction mixture was stirred at ambient temperatureovernight. The reaction mixture was then partitioned between ethylacetate and water. The aqueous phase was extracted twice with ethylacetate. The combined organic fractions were washed with brine, driedover MgSO₄ and concentrated. The residue was purified by flashchromatography on a Teledyne Isco CombiFlash® apparatus using a RediSep®silica gel cartridge (4 g) eluted with 0-10% methanol/dichloromethane.The residue was treated with ethyl acetate, and the precipitate wascollected by vacuum filtration and dried in a vacuum oven to give thetitled compound (5 mg, yield 9%).

¹H NMR (600 MHz, DMSO-d₆) δ ppm 8.48 (t, J=5.5 Hz, 2H), 8.06 (dd, J=8.8,2.2 Hz, 2H), 7.94 (d, J=2.3 Hz, 1H), 7.41 (s, 5H), 7.31 (d, J=8.8 Hz,2H), 6.33 (q, J=7.0 Hz, 2H), 2.59 (s, 3H), 1.75 (d, J=7.0 Hz, 5H), 1.13(t, J=7.2 Hz, 5H).

Determination of Biological Activity

Abbreviations: EGTA for ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid; GABA forγ-aminobutyric acid; GTPgS for guanosine 5′-O-[gamma-thio]triphosphate;and Tris for tris(hydroxymethyl)aminomethane.

Preparation of Rat Brain Membranes for Native Receptor Assays

Membranes from rat brain cortex were prepared as described in detail byOlpe et al. and stored at concentrations of 1.66 mg/mL protein at −80°C. until required. (Olpe, H.-R, et al. Eur J Pharmacol 1990; 187:27-38).

[³⁵S] GTPgS Binding Assay

The composition of the assay mixtures [in a final volume of 200 μL in96-well U-bottom plates (Greiner) was as follows: 50 mM Tris-HCl buffer,pH 7.7, 10 mM MgCl₂, 0.2 mM EGTA, 2 mM CaCl₂, 100 mM NaCl, 20 μMguanosine 5′-diphosphate (Sigma), 0.3 nM [³⁵S]GTPgS (1250 Ci/mmol(PerkinElmer)), and the test compounds at increasing concentrations(from 10 nM up to 10 μM), 10 μg of rat cortical membranes, and aconcentration of 1 μM GABA, that has been observed in previousexperiments to correspond to the EC₂₅, a concentration that gives 25% ofthe maximal response of GABA. The samples were incubated at roomtemperature for 60 minutes on a shaker. The incubation was stopped byrapid vacuum filtration over glass-fiber filter plates (UniFilter-96well, GF/B membrane plates, PerkinElmer) using a 96-well plate harvester(TOMTEK© Harvester). The UniFilter plate was washed five times withice-cold wash buffer (50 mM Tris-HCl buffer, pH 7.7, 10 mM MgCl₂, and100 mM NaCl. After filtration the plate was dried for 90 minutes at 55°C. The plates were closed on the bottom with black sealing membranes,and liquid scintillation cocktail (35 Betaplate Scint, PerkinElmer) wasadded to each well. After sealing the top of the plate, an additionalincubation step of 90 minutes at room temperature followed beforemeasuring the plate. The amount of membrane-bound [³⁵S]GTPgS wasmeasured using a 96-well plate reader (Microbeta®, PerkinElmer).Nonspecific binding was measured in the presence of unlabeled 10 μM ofGTPgS (Millipore) and without GABA. Basal binding was measured in theabsence of 1 μM GABA, and maximal binding was measured in the presenceof GABA using 1 mM GABA concentrations.

Data analysis. The concentration-response curves of compounds of thepresent disclosure in the presence of EC₂₅ of GABA-B receptor agonistwere generated using the GraphPad Prism® program (GraphPad Software, SanDiego, Calif.). Data was normalized using basal binding as 0% andmaximal binding as 100%. The curves were fitted by nonlinear regressionallowing determination of EC₅₀ values from sigmoidal dose-responsecurves. Each curve was performed using triplicate sample per date pointand 10 concentrations.

GTPgS Binding Example EC₅₀ (μM) 1 0.051 2 >10 3 >10 4 1.66 6 1.96 7 0.68 2.11 10 1.06 11 >10 12 0.347 13 3.54 14 2.13 16 0.222 18 0.389 19 1.5821 0.229 22 2.69 23 >10 24 1.85 27 3.2 28 3.47 31 1.81 33 >10 34 4.81 350.562 36 0.895 37 3.67 38 0.643 39 0.105 40 >10 41 4.67 42 9.64 45 0.37646 2.29 47 0.578 48 1.55 49 0.283 51 1.5 52 >10 53 0.62 54 1.2 55 0.0856 0.982 57 3.33 58 >10 59 0.017 60 >10 61 >10 63 0.491 64 0.644 65 1.8566 2.79 67 2.13 68 0.048 70 0.935 71 2.21 72 7.7 73 0.039 74 3.41 751.76 76 1.93 77 2.48 78 6.35 79 0.511 82 0.023 83 3.09 85 2.62 86 2.7687 1.03 89 1.39 91 2.12 95 1.74 96 2.59 97 1.85 98 0.45 100 0.667 1013.71 102 0.846 103 0.439 105 0.033 106 0.847 107 1.47 109 1.21 111 >10112 3.63 113 3.84 114 3.8 115 4.12 116 0.855 117 0.043 118 2.93 1190.056 120 6.82 122 3.8 125 0.582 126 0.501 127 1.56 128 >10 129 2.11 1310.453

It is understood that the foregoing detailed description andaccompanying examples are merely illustrative and are not to be taken aslimitations upon the scope of the invention, which is defined solely bythe appended claims and their equivalents. Various changes andmodifications to the described embodiments will be apparent to thoseskilled in the art. Such changes and modifications, including withoutlimitation those relating to the chemical structures, substituents,derivatives, intermediates, syntheses, formulations, or methods, or anycombination of such changes and modifications of use of the invention,may be made without departing from the spirit and scope thereof.

What is claimed is:
 1. A compound of formula (I):

or a pharmaceutically acceptable salt or isotopically labelled formthereof, wherein: X is O or S; R¹ is selected from the group consistingof C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, C₃-C₆cycloalkyl, and phenyl;wherein, C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,partly or completely fluorinated and/or substituted with one or moresubstituents independently selected from the group consisting ofC₁-C₆alkoxy, fluoroC₁-C₆alkoxy, hydroxy, and oxo; C₃-C₆cycloalkyl isoptionally substituted with one or more substituents independentlyselected from the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluorine,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, hydroxy, and oxo; phenyl isoptionally substituted with one or more substituents selected from thegroup consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl,fluoroC₁-C₆alkoxy, and halo; R² is selected from the group consisting ofC₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl, and —(CR^(a)R^(b))_(n)-G¹;wherein, C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted,partly or completely fluorinated and/or substituted with one or moresubstituents independently selected from the group consisting ofC₁-C₆alkoxy, fluoroC₁-C₆alkoxy, hydroxy, and oxo; R^(a) and R^(b) areindependently selected at each occurrence from the group consisting ofhydrogen, fluorine, C₁-C₆alkyl, fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, andphenyl; wherein phenyl is optionally substituted with one or moresubstituents selected from the group consisting of C₁-C₆alkyl,C₁-C₆alkoxy, fluoroC₁-C₆alkoxy, fluoroC₁-C₆alkyl, and halo; n is 1, 2 or3; G¹ is selected from the group consisting of phenyl, bicyclicaryl,monocyclic heteroaryl, and bicyclic heteroaryl; wherein the phenyl, thebicyclicaryl, the monocyclic heteroaryl, and the bicyclic heteroaryl areoptionally substituted with 1, 2, 3 or 4 substituents independentlyselected from the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, cyano,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, halo, and hydroxy; R³ is selectedfrom the group consisting of C₁-C₆alkyl, C₃-C₆cycloalkyl, phenyl,phenylC₁-C₆alkyl, bicyclicaryl, bicyclicarylC₁-C₆alkyl, monocyclicheteroarylC₁-C₆alkyl, monocyclic heteroaryl, and bicyclic heteroaryl;wherein C₁-C₆alkyl is unsubstituted, partly or completely fluorinatedand/or substituted with one or more substituents independently selectedfrom the group consisting of C₁-C₆alkoxy, fluoroC₁-C₆alkoxy, hydroxy,and oxo; C₃-C₆cycloalkyl is optionally substituted with one or moresubstituents independently selected from the group consisting ofC₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkoxy, fluorine, hydroxy, and oxo;and phenyl, phenyl of phenylC₁-C₆alkyl, bicyclicaryl, bicyclicaryl ofbicyclicarylC₁-C₆alkyl, monocyclic heteroaryl of monocyclicheteroarylC₁-C₆alkyl, monocyclic heteroaryl and bicyclic heteroaryl areoptionally substituted with 1, 2, 3 or 4 substituents R^(Ar), which areindependently selected from the group consisting of C₁-C₆alkyl,C₂-C₆alkenyl, C₂-C₆alkynyl, halogen, cyano, —OR^(1a), —OC(O)R^(1a),—OC(O)N(R^(d))(R^(3a)), —SR^(1a), —S(O)₂R^(2a), —S(O)₂N(R^(d))(R^(3a)),—C(O)R^(1a), —C(O)OR^(1a), —C(O)N(R^(d))(R^(3a)), —N(R^(d))(R^(3a)),—N(R^(c))C(O)R^(1a), —N(R^(c))S(O)₂R^(2a), —N(R^(c))C(O)O(R^(1a)),—N(R^(c))C(O)N(R^(d))(R^(3a)), —(CR^(4a)R^(5a))_(m)—OR^(1a),—(CR^(4a)R^(5a))_(m)—OC(O)R^(1a),—(CR^(4a)R^(5a))_(m)—OC(O)N(R^(d))(R^(3a)),—(CR^(4a)R^(5a))_(m)—SR^(1a), —(CR^(4a)R^(5a))_(m)—S(O)₂R^(2a),—(CR^(4a)R^(5a))_(m)—S(O)₂N(R^(d))(R^(3a)),—(CR^(4a)R^(5a))_(m)—C(O)R^(1a), —(CR^(4a)R^(5a))_(m)—C(O)OR^(1a),—(CR^(4a)R^(5a))_(m)—C(O)N(R^(d))(R^(3a)),—(CR^(4a)R^(5a))_(m)—N(R^(d))(R^(3a)),—(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)R^(1a),—(CR^(4a)R^(5a))_(m)—N(R^(c))S(O)₂R^(2a),—(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)O(R^(1a)),—(CR^(4a)R^(5a))_(m)—N(R^(c))C(O)N(R^(d))(R^(3a)), cyanoC₁-C₆-alkyl andfluoroC₁-C₆-alkyl; m is 1, 2, 3, or 4; R^(c) and R^(d), at eachoccurrence, are each independently hydrogen, C₁-C₆alkyl, orfluoroC₁-C₆-alkyl; R^(1a) and R^(3a), at each occurrence, are eachindependently hydrogen, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl; R^(d) andR^(3a), if present as a group N(R^(d))(R^(3a)), may together with thenitrogen atom of N(R^(d))(R^(3a)) also form an N-bound saturated 3 to 8membered heterocycle, which in addition to the nitrogen atom may have 1or 2 further heteroatoms as ring members, which are selected from O, Sand N; R^(c) and R^(1a), if present as a group —N(R^(c))C(O)R^(1a), maytogether with the atoms of said moiety form an N-bound saturated 3 to 8membered heterocycle, which has an oxo group in 2-position and which inaddition to the nitrogen atom may have 1 or 2 further heteroatoms asring members, which are selected from O, S and N; and R^(2a), at eachoccurrence, is independently C₁-C₆alkyl, or fluoroC₁-C₆-alkyl; andR^(4a) and R^(5a), at each occurrence, are each independently hydrogen,fluorine, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl, except for the followinggroups of compounds and except for their pharmaceutically acceptablesalts: compounds of formula (I), where X is O, R¹ is methyl, R² ismethyl, ethyl, n-butyl, unsubstituted benzyl, prop-2-ynyl,2-(ethoxycarbonyl)ethyl or 2-carboxyethyl and R³ is unsubstitutedphenyl; compounds of formula (I), where X is O, R¹ is methyl, R² ismethyl, 2,2,2-trifluoroacetyl or unsubstituted benzyl, and R³ is methyl;compounds of formula (I), where X is O, R¹ is methyl, R² isethoxycarbonylmethyl and R³ is unsubstituted benzyl, or 4-methoxybenzyl.2. The compound or pharmaceutically acceptable salt or isotopicallylabelled form thereof of claim 1, wherein R¹ is selected from the groupconsisting of C₁-C₆alkyl, C₂-C₆alkenyl, C₂-C₆alkynyl andC₃-C₆cycloalkyl; wherein, C₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl areunsubstituted, partly or completely fluorinated and/or substituted withone or two substituents independently selected from the group consistingof C₁-C₆alkoxy, hydroxy, and oxo; and C₃-C₆cycloalkyl is unsubstitutedor substituted with 1, 2, 3, 4 or 5 substituents independently selectedfrom the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluorine,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, hydroxy, and oxo.
 3. The compoundor pharmaceutically acceptable salt or isotopically labelled formthereof of claim 2, wherein R¹ is selected from the group consisting ofC₁-C₆alkyl, fluoroC₁-C₆alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl and cyclopropyl,wherein cyclopropyl is unsubstituted or substituted with 1 or 2substituents independently selected from the group consisting ofC₁-C₃alkyl, fluorine, and fluoroC₁-C₃alkyl.
 4. The compound orpharmaceutically acceptable salt or isotopically labelled form thereofof claim 1; wherein R¹ is phenyl; wherein phenyl is optionallysubstituted with 1, 2, 3 or 4 substituents selected from the groupconsisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl,fluoroC₁-C₆alkoxy, and halo.
 5. The compound or pharmaceuticallyacceptable salt or isotopically labelled form thereof of claim 1,wherein R¹ is selected from the group consisting of methyl, ethyl,isopropyl, n-propyl, cyclopropyl, methoxymethyl, phenyl which isunsubstituted or substituted by halo.
 6. The compound orpharmaceutically acceptable salt or isotopically labelled form thereofof claim 1, wherein R² is selected from the group consisting ofC₁-C₆alkyl, C₂-C₆alkenyl, and C₂-C₆alkynyl; wherein C₁-C₆alkyl,C₂-C₆alkenyl, and C₂-C₆alkynyl are unsubstituted, partly or completelyfluorinated and/or substituted with one or two substituentsindependently selected from the group consisting of C₁-C₆alkoxy,hydroxy, and oxo.
 7. The compound or pharmaceutically acceptable salt orisotopically labelled form thereof of claim 6, wherein, R² is C₁-C₆alkylor fluoroC₁-C₆alkyl.
 8. The compound or pharmaceutically acceptable saltor isotopically labelled form thereof of claim 1, wherein R² is—(CR^(a)R^(b))_(n)-G¹.
 9. The compound or pharmaceutically acceptablesalt or isotopically labelled form thereof of claim 8; wherein G¹ isselected from the group consisting of phenyl and monocyclic heteroaryl;wherein the phenyl and the monocyclic heteroaryl are optionallysubstituted with 1, 2, 3 or 4 substituents independently selected fromthe group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, cyano,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, halo, and hydroxy.
 10. The compoundor pharmaceutically acceptable salt or isotopically labelled formthereof of claim 9, wherein G¹ is phenyl, which is optionallysubstituted with 1, 2, 3 or 4 substituents independently selected fromthe group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluoroC₁-C₆alkyl,fluoroC₁-C₆alkoxy, halo, and hydroxy.
 11. The compound orpharmaceutically acceptable salt or isotopically labelled form thereofof claim 8, wherein R^(a) and R^(b) are independently selected at eachoccurrence from the group consisting of hydrogen, C₁-C₆alkyl and phenyl;wherein phenyl is optionally substituted with 1, 2 or 3 substituentsselected from the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, and halo; and n is 1 or
 2. 12. Thecompound or pharmaceutically acceptable salt or isotopically labelledform thereof of claim 11, wherein the moiety —(CR^(a)R^(b))_(n)— is CH₂,CH₂CH₂, CH(CH₃) or CH(phenyl).
 13. The compound or pharmaceuticallyacceptable salt or isotopically labelled form thereof of claim 12,wherein the moiety —(CR^(a)R^(b))_(n)— is CH(CH₃), which haspredominately R-configuration.
 14. The compound or pharmaceuticallyacceptable salt or isotopically labelled form thereof of claim 1,wherein R² is selected from the group consisting of4-chlorophenylmethyl, 3-(trifluoromethyl)phenylmethyl,4-(trifluoromethyl)phenylmethyl,4-methoxy-3-(trifluoromethyl)phenylmethyl,2-fluoro-5-(trifluoromethyl)phenylmethyl, 5-chloro-2-fluorophenylmethyl,4-chloro-2-fluorophenylmethyl, 4-chlorophenylphenylmethyl,2,4-difluorophenylmethyl, 4-fluoro-3-(trifluoromethyl)phenylmethyl,4-chloro-3-(trifluoromethyl)phenylmethyl, 2-fluorophenylmethyl,4-fluorophenylmethyl, 1-(4-chlorophenyl)ethyl, 2-(4-chlorophenyl)ethyl,1-(4-(trifluoromethyl)phenyl)ethyl, 4-pyridylmethyl and 3-methylbutyl.15. The compound or pharmaceutically acceptable salt or isotopicallylabelled form thereof of claim 1 wherein R³ is selected from the groupconsisting of C₁-C₆alkyl and C₃-C₆cycloalkyl; wherein C₁-C₆alkyl isunsubstituted, partly or completely fluorinated and/or substituted withone or two substituents independently selected from the group consistingof C₁-C₆alkoxy, hydroxy, and oxo; and C₃-C₆cycloalkyl is unsubstitutedor substituted with 1, 2, 3, 4 or 5 substituents independently selectedfrom the group consisting of C₁-C₆alkyl, C₁-C₆alkoxy, fluorine,fluoroC₁-C₆alkyl, fluoroC₁-C₆alkoxy, hydroxy, and oxo.
 16. The compoundor pharmaceutically acceptable salt or isotopically labelled formthereof of claim 15, wherein R³ is C₁-C₆alkyl or fluoroC₁-C₆alkyl. 17.The compound or pharmaceutically acceptable salt or isotopicallylabelled form thereof of claim 1, wherein R³ is selected from the groupconsisting of phenyl, phenylC₁-C₆alkyl, bicyclicaryl,bicyclicarylC₁-C₆alkyl, monocyclic heteroarylC₁-C₆alkyl, monocyclicheteroaryl, and bicyclic heteroaryl; wherein the phenyl, the phenyl ofphenylC₁-C₆alkyl, the bicyclicaryl, the bicyclicaryl ofbicyclicarylC₁-C₆alkyl, the monocyclic heteroaryl of monocyclicheteroarylC₁-C₆alkyl, the monocyclic heteroaryl and the bicyclicheteroaryl are optionally substituted with 1, 2, 3 or 4 substituentsR^(Ar).
 18. The compound or pharmaceutically acceptable salt orisotopically labelled form thereof of claim 17, wherein R³ is selectedfrom the group consisting of phenyl and monocyclic heteroaryl; whereinphenyl is substituted with 1, 2, 3 or 4 substituents R^(Ar) and wherethe monocyclic heteroaryl is unsubstituted or substituted with 1, 2, 3or 4 substituents R^(Ar).
 19. The compound or pharmaceuticallyacceptable salt or isotopically labelled form thereof of claim 1,wherein R^(Ar), independently of its occurrence, is selected from thegroup consisting of C₁-C₆alkyl, halogen, —OR^(1a),—S(O)₂N(R^(d))(R^(3a)), —C(O)R^(1a), —C(O)OR^(1a),—C(O)N(R^(d))(R^(3a)), —N(R^(d))(R^(3a)), —N(R^(c))C(O)R^(1a),—N(R^(c))S(O)₂R^(2a) and fluoroC₁-C₆-alkyl; wherein R^(c) and R^(d), ateach occurrence, are each independently hydrogen, C₁-C₆alkyl, orfluoroC₁-C₆-alkyl; R^(1a) and R^(3a), at each occurrence, are eachindependently hydrogen, C₁-C₆alkyl, or fluoroC₁-C₆-alkyl; or R^(d) andR^(3a), if present as a group N(R^(d))R^(3a), may together with thenitrogen atom of said moiety form an N-bound pyrrolidin, N-boundpiperidin or N-bound azepan radical; and R^(2a), at each occurrence, isindependently C₁-C₆alkyl, or fluoroC₁-C₆-alkyl.
 20. The compound orpharmaceutically acceptable salt or isotopically labelled form thereofof claim 1, wherein R³ is selected from the group consisting of methyl,ethyl, phenyl, 3-fluorophenyl, 4-fluorophenyl, 2-aminophenyl,3-aminophenyl, 2-hydroxyphenyl, 2-methylphenyl, 2-methoxyphenyl,4-methoxyphenyl, 3-carbamoylphenyl, 3-(acetylamino)phenyl,3-(methylsulfonylamino)phenyl, 3-(aminosulfonyl)phenyl,3,4-difluorophenyl, 3,5-difluorophenyl, 2,4-bis(methoxy)phenyl,3,4-bis(methoxy)phenyl, 2,5-bis(methoxy)phenyl,2-methoxy-5-fluorophenyl, 2-amino-5-fluorophenyl,2-methoxy-5-carboxyphenyl, 2-methoxy-5-(trifluoromethyl)phenyl,2-methoxy-5-(acetylamino)phenyl, 2-methoxy-3-(acetylamino)phenyl,2-(trifluoromethoxy)-5-(acetylamino)phenyl,2-methoxy-5-(methylsulfonylamino)phenyl,4-fluoro-3-(acetylamino)phenyl,2-methyl-5-(acetylamino)phenyl, 2-methyl-5-hydroxyphenyl,2-methoxy-5-(aminocarbonyl)phenyl, 3-amino-2-(aminocarbonyl)phenyl,2-methoxy-5-(N-methylaminocarbonyl)phenyl,2-methoxy-5-(N-ethylaminocarbonyl)phenyl,2-methoxy-5-(N,N-dimethylaminocarbonyl)phenyl,2-methoxy-5-(pyrrolidin-1-ylcarbonyl)phenyl,2-methoxy-5-(pyrrolidin-2on-1-yl)phenyl,3-methoxy-5-(N,N-dimethylaminocarbonyl)phenyl, 2-amino-5-chlorophenyl,2-amino-5-(trifluoromethyl)phenyl, 2-amino-3,5-difluorophenyl,2-methyl-3-(acetylamino)-4-fluorophenyl, 3-pyridyl, 5-pyrimidinyl,2-fluoro-3-pyridyl, 2-amino-4-pyridyl, 5-fluoro-3-pyridyl,2-chloro-3-pyridyl, indol-5-yl, 2,6-difluoropyridin-4-yl, 2-thienyl,1-ethylpyrazol-5-yl, and 1H-pyrrolo[2,3-b]pyridine-6-yl.
 21. Thecompound or pharmaceutically acceptable salt or isotopically labelledform thereof of claim 1, wherein X is O.
 22. A compound selected fromthe group consisting of:N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;5-(4-chlorobenzyl)-7-(4-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;5-[1-(4-chlorophenyl)ethyl]-7-(2,6-difluoropyridin-4-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,4-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2-amino-5-chlorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-(2-chloropyridin-3-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{5-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-2-fluorophenyl}acetamide;7-(2,5-dimethoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[2-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-[2-amino-5-(trifluoromethyl)phenyl]-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-(1H-indol-6-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-(propan-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2-aminophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;5-[1-(4-chlorophenyl)ethyl]-7-(5-hydroxy-2-methylphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(2-fluoro-5-{5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methylphenyl)acetamide;7-(4-fluorophenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-(5-fluoropyridin-3-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(3-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)methanesulfonamide;5-[2-fluoro-5-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2-methoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-3-(methoxymethyl)-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;5-[4-chloro-3-(trifluoromethyl)benzyl]-7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(2-fluoro-5-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;5-(4-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[(1S)-1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,4-dimethoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-2-methoxyphenyl)acetamide;N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;N-[4-methyl-3-(3-methyl-4-oxo-5-{(1R)-1[4-(trifluoromethyl)phenyl]ethyl}1-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-ethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,4-dimethoxyphenyl)-5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N,N-dimethylbenzamide;N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;N-(3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;N-(3-{5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;5-(4-chlorobenzyl)-7-(3,4-difluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[4-fluoro-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3,7-dimethyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]-4-methoxyphenyl}acetamide;5-[2-fluoro-5-(trifluoromethyl)benzyl]-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,4-dimethoxyphenyl)-5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-[3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-(trifluoromethoxy)phenyl]acetamide;5-[4-methoxy-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-3-cyclopropyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-propyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzenesulfonamide;5-[4-fluoro-3-(trifluoromethyl)benzyl]-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)methanesulfonamide;5-(4-chlorobenzyl)-3-methyl-7-(thiophen-2-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;5-[(1R)-1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzamide;5-[2-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(2-fluoro-5-{5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;N-(2-fluoro-5-{5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;5-[1-(4-chlorophenyl)ethyl]-7-(5-fluoro-2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(4-methoxy-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;2-amino-6-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamide;7-(4-fluorophenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(2-methoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[(1S)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[4-chloro-3-(trifluoromethyl)benzyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-(methoxymethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxybenzoicacid;7-(4-fluorophenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[(R)-(4-chlorophenyl)(phenyl)methyl]-3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-3-methyl-7-(2-methylphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2-amino-3,5-difluorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;5-[1-(4-chlorophenyl)ethyl]-7-[2-methoxy-5-(trifluoromethyl)phenyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,5-dimethoxyphenyl)-5-[4-fluoro-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide;5-(4-chlorobenzyl)-7-(4-fluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(3-chloro-4-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;7-(2-aminopyridin-3-yl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(2,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(5-chloro-2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[(S)-(4-chlorophenyl)(phenyl)methyl]-3,7-diethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(3,5-difluorophenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-4-oxo-3-propyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;5-(4-chloro-2-fluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,5-dimethoxyphenyl)-3-methyl-5-(pyridin-4-ylmethyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{2-fluoro-5-[3-methyl-4-oxo-5-(pyridin-4-ylmethyl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;7-(2,5-dimethoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-4-oxo-3-(propan-2-yl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;7-(2-amino-5-fluorophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-[2-methoxy-5-(pyrrolidin-1-ylcarbonyl)phenyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-7-(3,4-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-(2-hydroxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2-methoxyphenyl)-5-[4-methoxy-3-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;-(4-chlorobenzyl)-7-(2,5-dimethoxyphenyl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1S)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;N-{3-[5-(4-chlorobenzyl)-4-oxo-3-phenyl-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;N-[4-methoxy-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}benzamide;N-(4-methyl-3-{3-methyl-4-oxo-5-[4-(trifluoromethyl)benzyl]-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}phenyl)acetamide;3,7-dimethyl-5-(3-methylbutyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(pyridin-3-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[3-methyl-4-oxo-5-(pyridin-4-ylmethyl)-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;3-{5-[(1R)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide;N-[6-fluoro-2-methyl-3-(3-methyl-4-oxo-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl)phenyl]acetamide;5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(pyrimidin-5-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-7-(1-ethyl-1H-pyrazol-5-yl)-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[1-(4-chlorophenyl)ethyl]-3-methyl-7-(1H-pyrrolo[3,2-b]pyridin-6-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-(3-{5-[(1S)-1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxyphenyl)acetamide;7-(2-methoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-4-methoxy-N-methylbenzamide;5-(4-chlorobenzyl)-3-methyl-7-(pyridin-3-yl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3,7-dimethyl-5-[3-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(4-chlorobenzyl)-3-methyl-7-phenyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-(2,4-difluorobenzyl)-3,7-dimethyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3,7-dimethyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,5-dimethoxyphenyl)-3-methyl-5-{(1R)-1-[4-(trifluoromethyl)phenyl]ethyl}[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(3-aminophenyl)-5-[1-(4-chlorophenyl)ethyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;7-(2,4-dimethoxyphenyl)-3-methyl-5-[4-(trifluoromethyl)benzyl][1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;5-[(1R)-1-(4-chlorophenyl)ethyl]-3-cyclopropyl-7-(2,5-dimethoxyphenyl)[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;N-{3-[5-(4-chlorobenzyl)-3-ethyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl]phenyl}acetamide;7-(2,5-dimethoxyphenyl)-5-[2-fluoro-5-(trifluoromethyl)benzyl]-3-methyl[1,2]oxazolo[4,5-d]pyridazin-4(5H)-one;3-{5-[1-(4-chlorophenyl)ethyl]-3-methyl-4-oxo-4,5-dihydro[1,2]oxazolo[4,5-d]pyridazin-7-yl}-N-ethyl-4-methoxybenzamide;the pharmaceutically acceptable salts thereof and the isotopicallylabelled forms thereof.
 23. A pharmaceutical composition comprising atherapeutically effective amount of a compound or pharmaceuticallyacceptable salt or isotopically labelled form thereof of claim 1 incombination with a pharmaceutically acceptable carrier, diluent, orexcipient.
 24. A method of selectively modulating a disorder orcondition, which is selected from the group consisting of pain,substance abuse (especially in alcohol dependence), depression,spasticity, fragile X syndrome, Down's syndrome, autism, retinalganglion cell degeneration, gastro-esophageal reflux disease (GERD),smoking cessation, addiction of narcotic agents, emesis, cough,overactive bladder, anxiety, migraine and tinnitus in a mammalcomprising administering an effective amount of a compound orpharmaceutically acceptable salt or isotopically labelled form thereofof claim
 1. 25. A method of treating a condition or disorder modulatedby the γ-aminobutyric acid B (GABA-B) receptor in a mammal comprisingadministering an effective amount of a compound or pharmaceuticallyacceptable salt or isotopically labelled form thereof of claim
 1. 26.The method of claim 25, where the condition or disorder is selected fromthe group consisting of pain, substance abuse (especially in alcoholdependence), depression, spasticity, fragile X syndrome, Down'ssyndrome, autism, retinal ganglion cell degeneration, gastro-esophagealreflux disease (GERD), smoking cessation, addiction of narcotic agents,emesis, cough, overactive bladder, anxiety, migraine and tinnitus.